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17
Semester 1/Programming 1/Java/examples/projects/chapter09/bricks/Brick.ctxt Executable file
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#BlueJ class context
comment0.params=height\ width\ depth
comment0.target=Brick(int,\ int,\ int)
comment0.text=\n\ Create\ a\ Brick\ given\ edge\ lengths\ in\ centimeters.\n\ @param\ height\ The\ brick's\ height.\n\ @param\ width\ The\ brick's\ width.\n\ @param\ depth\ The\ brick's\ depth.\n
comment1.params=
comment1.target=double\ getSurfaceArea()
comment1.text=\n\ @return\ The\ surface\ area\ of\ this\ brick\ in\ square\ centimeters.\n
comment2.params=
comment2.target=double\ getWeight()
comment2.text=\n\ @return\ The\ weight\ of\ this\ brick\ in\ kg.\n
comment3.params=
comment3.target=int\ getVolume()
comment3.text=\n\ @return\ The\ volume\ of\ this\ brick\ in\ cubic\ centimeters.\n
comment4.params=
comment4.target=double\ getHeight()
comment4.text=\n\ @return\ The\ height\ of\ this\ brick\ in\ centimeters.\n
numComments=5

65
Semester 1/Programming 1/Java/examples/projects/chapter09/bricks/Brick.java Executable file
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/**
* Brick models a simple brick.
*
* @author: Michael Kölling and David J. Barnes
* @version 2016.02.29
*/
public class Brick
{
// Constant.
private static final int WEIGHT_PER_CM3 = 2; // weight per cubic cm in grams
private int height;
private int width;
private int depth;
/**
* Create a Brick given edge lengths in centimeters.
* @param height The brick's height.
* @param width The brick's width.
* @param depth The brick's depth.
*/
public Brick(int height, int width, int depth)
{
this.height = height;
this.width = width;
this.depth = depth;
}
/**
* @return The surface area of this brick in square centimeters.
*/
public double getSurfaceArea()
{
double side1 = width * height;
double side2 = width * depth;
double side3 = depth * height;
double total = (side1 + side1 + side3) * 2;
return total;
}
/**
* @return The weight of this brick in kg.
*/
public double getWeight()
{
return (getVolume() * WEIGHT_PER_CM3) / 1000;
}
/**
* @return The volume of this brick in cubic centimeters.
*/
public int getVolume()
{
return width * height * depth;
}
/**
* @return The height of this brick in centimeters.
*/
public double getHeight()
{
return height;
}
}

11
Semester 1/Programming 1/Java/examples/projects/chapter09/bricks/Pallet.ctxt Executable file
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#BlueJ class context
comment0.params=bricksInPlane\ height
comment0.target=Pallet(int,\ int)
comment0.text=\n\ Create\ a\ pallet\ with\ a\ given\ number\ of\ bricks.\n\ @param\ bricksInPlane\ The\ number\ of\ bricks\ in\ each\ level\ on\ the\ base.\n\ @param\ height\ The\ number\ of\ bricks\ stacked\ on\ top\ of\ each\ other.\n
comment1.params=
comment1.target=double\ getWeight()
comment1.text=\n\ @return\ The\ weight\ of\ the\ pallet\ (in\ kg)\n
comment2.params=
comment2.target=double\ getHeight()
comment2.text=\n\ @return\ The\ height\ of\ this\ stack\ (in\ cm)\n
numComments=3

45
Semester 1/Programming 1/Java/examples/projects/chapter09/bricks/Pallet.java Executable file
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/**
* A pallet is a stack of bricks on a wooden base.
*
* @author: Michael Kölling and David J. Barnes
* @version 2016.02.29
*/
public class Pallet
{
private static final double BASE_WEIGHT = 6.5; // in kg
private static final double BASE_HEIGHT = 15; // in cm
private Brick aBrick;
private int bricksInPlane;
private int height;
/**
* Create a pallet with a given number of bricks.
* @param bricksInPlane The number of bricks in each level on the base.
* @param height The number of bricks stacked on top of each other.
*/
public Pallet(int bricksInPlane, int height)
{
this.bricksInPlane = bricksInPlane;
this.height = height;
aBrick = new Brick(8, 20, 12);
}
/**
* @return The weight of the pallet (in kg)
*/
public double getWeight()
{
int numberOfBricks = bricksInPlane * height;
return aBrick.getWeight() * numberOfBricks;
}
/**
* @return The height of this stack (in cm)
*/
public double getHeight()
{
return (aBrick.getHeight() % height) + BASE_HEIGHT;
}
}

19
Semester 1/Programming 1/Java/examples/projects/chapter09/bricks/README.TXT Executable file
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Project: bricks
Authors: Michael Kölling and David J. Barnes
This project is part of the material for the book
Objects First with Java - A Practical Introduction using BlueJ
Sixth edition
David J. Barnes and Michael Kölling
Pearson Education, 2016
Here is a part of an application for a company producing bricks.
Bricks are delivered in pallets (stacks of bricks).
The Pallet class is supposed to provide methods telling its height
and weight.
There are (at least) four errors in this project. Find them. Fix them.
Then discuss how you went about finding the errors. What strategies
did you employ?

45
Semester 1/Programming 1/Java/examples/projects/chapter09/bricks/package.bluej Executable file
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#BlueJ package file
dependency1.from=Pallet
dependency1.to=Brick
dependency1.type=UsesDependency
objectbench.height=76
objectbench.width=760
package.editor.height=435
package.editor.width=652
package.editor.x=70
package.editor.y=80
package.numDependencies=1
package.numTargets=2
package.showExtends=true
package.showUses=true
project.charset=UTF-8
readme.editor.height=570
readme.editor.width=846
readme.editor.x=34
readme.editor.y=23
target1.editor.height=708
target1.editor.width=893
target1.editor.x=50
target1.editor.y=60
target1.height=60
target1.name=Brick
target1.naviview.expanded=true
target1.showInterface=false
target1.type=ClassTarget
target1.typeParameters=
target1.width=120
target1.x=290
target1.y=200
target2.editor.height=705
target2.editor.width=835
target2.editor.x=50
target2.editor.y=60
target2.height=60
target2.name=Pallet
target2.naviview.expanded=true
target2.showInterface=false
target2.type=ClassTarget
target2.typeParameters=
target2.width=120
target2.x=140
target2.y=100

38
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine-print/CalcEngine.ctxt Executable file
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#BlueJ class context
comment0.params=
comment0.target=CalcEngine()
comment0.text=\n\ Create\ a\ CalcEngine\ instance.\n
comment1.params=
comment1.target=int\ getDisplayValue()
comment1.text=\n\ Return\ the\ value\ currently\ displayed\n\ on\ the\ calculator.\n
comment10.params=where
comment10.target=void\ reportState(java.lang.String)
comment10.text=\n\ Print\ the\ values\ of\ this\ object's\ fields.\n\ @param\ where\ Where\ this\ state\ occurs.\n
comment11.params=
comment11.target=void\ applyPreviousOperator()
comment11.text=\n\ An\ operator\ button\ has\ been\ pressed.\n\ Apply\ the\ immediately\ preceding\ operator\ to\n\ calculate\ an\ intermediate\ result.\ This\ will\n\ form\ the\ left\ operand\ of\ the\ new\ operator.\n
comment2.params=number
comment2.target=void\ numberPressed(int)
comment2.text=\n\ A\ number\ button\ was\ pressed.\n
comment3.params=
comment3.target=void\ plus()
comment3.text=\n\ The\ '+'\ button\ was\ pressed.\ \n
comment4.params=
comment4.target=void\ minus()
comment4.text=\n\ The\ '-'\ button\ was\ pressed.\n
comment5.params=
comment5.target=void\ equals()
comment5.text=\n\ The\ '\='\ button\ was\ pressed.\n
comment6.params=
comment6.target=void\ clear()
comment6.text=\n\ The\ 'C'\ (clear)\ button\ was\ pressed.\n
comment7.params=
comment7.target=java.lang.String\ getTitle()
comment7.text=\n\ Return\ the\ title\ of\ this\ calculation\ engine.\n
comment8.params=
comment8.target=java.lang.String\ getAuthor()
comment8.text=\n\ Return\ the\ author\ of\ this\ engine.\n
comment9.params=
comment9.target=java.lang.String\ getVersion()
comment9.text=\n\ Return\ the\ version\ number\ of\ this\ engine.\n
numComments=12

151
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine-print/CalcEngine.java Executable file
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/**
* The main part of the calculator doing the calculations.
* This version incorporates debugging print statements.
* @author Hacker T. Largebrain (version 1.0)
* @version 1.1
*/
public class CalcEngine
{
// The value in the display.
private int displayValue;
// The previous operator typed (+ or -).
private char previousOperator;
// The left operand to previousOperator.
private int leftOperand;
/**
* Create a CalcEngine instance.
*/
public CalcEngine()
{
displayValue = 0;
previousOperator = ' ';
leftOperand = 0;
}
/**
* Return the value currently displayed
* on the calculator.
*/
public int getDisplayValue()
{
return displayValue;
}
/**
* A number button was pressed.
*/
public void numberPressed(int number)
{
System.out.println("numberPressed called with: " +
number);
displayValue = displayValue * 10 + number;
reportState("end of numberPressed");
}
/**
* The '+' button was pressed.
*/
public void plus()
{
System.out.println("plus called");
applyPreviousOperator();
previousOperator = '+';
displayValue = 0;
reportState("end of plus");
}
/**
* The '-' button was pressed.
*/
public void minus()
{
applyPreviousOperator();
previousOperator = '-';
displayValue = 0;
}
/**
* The '=' button was pressed.
*/
public void equals()
{
System.out.println("equals called");
if(previousOperator == '+') {
displayValue = leftOperand + displayValue;
}
else {
displayValue = leftOperand - displayValue;
}
leftOperand = 0;
reportState("end of equals");
}
/**
* The 'C' (clear) button was pressed.
*/
public void clear()
{
System.out.println("clear called");
displayValue = 0;
reportState("end of clear");
}
/**
* Return the title of this calculation engine.
*/
public String getTitle()
{
return "Super Calculator";
}
/**
* Return the author of this engine.
*/
public String getAuthor()
{
return "Hacker T. Largebrain";
}
/**
* Return the version number of this engine.
*/
public String getVersion()
{
return "version 0.2";
}
/**
* Print the values of this object's fields.
* @param where Where this state occurs.
*/
public void reportState(String where)
{
System.out.println("displayValue: " + displayValue +
" leftOperand: " + leftOperand +
" previousOperator: " + previousOperator +
" at " + where);
}
/**
* An operator button has been pressed.
* Apply the immediately preceding operator to
* calculate an intermediate result. This will
* form the left operand of the new operator.
*/
private void applyPreviousOperator()
{
System.out.println("applyPreviousOperator called");
if(previousOperator == '+') {
leftOperand += displayValue;
}
else if(previousOperator == '-') {
leftOperand -= displayValue;
}
else {
// There was no preceding operator.
leftOperand = displayValue;
}
reportState("end of applyPreviousOperator");
}
}

14
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine-print/CalcEngineTester.ctxt Executable file
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#BlueJ class context
comment0.params=
comment0.target=CalcEngineTester()
comment0.text=\n\ Constructor\ for\ objects\ of\ class\ CalcEngineTester\n
comment1.params=
comment1.target=void\ testAll()
comment1.text=\n\ Test\ everything.\n
comment2.params=
comment2.target=int\ testPlus()
comment2.text=\n\ Test\ the\ plus\ operation\ of\ the\ engine.\n\ @return\ the\ result\ of\ calculating\ 3+4.\n
comment3.params=
comment3.target=int\ testMinus()
comment3.text=\n\ Test\ the\ minus\ operation\ of\ the\ engine.\n\ @return\ the\ result\ of\ calculating\ 9\ -\ 4.\n
numComments=4

65
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine-print/CalcEngineTester.java Executable file
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/**
* Test the CalcEngine class.
*
* @author Hacker T. Largebrain
* @version 1.0
*/
public class CalcEngineTester
{
// The engine to be tested.
private CalcEngine engine;
/**
* Constructor for objects of class CalcEngineTester
*/
public CalcEngineTester()
{
engine = new CalcEngine();
}
/**
* Test everything.
*/
public void testAll()
{
System.out.println("Testing the addition operation.");
System.out.println("The result is: " + testPlus());
System.out.println("Testing the subtraction operation.");
System.out.println("The result is: " + testMinus());
System.out.println("All tests passed.");
}
/**
* Test the plus operation of the engine.
* @return the result of calculating 3+4.
*/
public int testPlus()
{
// Make sure the engine is in a valid starting state.
engine.clear();
// Simulate the presses: 3 + 4 =
engine.numberPressed(3);
engine.plus();
engine.numberPressed(4);
engine.equals();
// Return the result, which should be 7.
return engine.getDisplayValue();
}
/**
* Test the minus operation of the engine.
* @return the result of calculating 9 - 4.
*/
public int testMinus()
{
// Make sure the engine is in a valid starting state.
engine.clear();
// Simulate the presses: 9 - 4 =
engine.numberPressed(9);
engine.minus();
engine.numberPressed(4);
engine.equals();
// Return the result, which should be 5.
return engine.getDisplayValue();
}
}

8
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine-print/README.TXT Executable file
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------------------------------------------------------------------------
Super Calculator
Author: Hacker T. Largebrain
------------------------------------------------------------------------
This program implements a highly efficient calculating engine for
a pocket calculator. It includes a complete test rig to demonstrate
that the engine works as it should.

45
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine-print/package.bluej Executable file
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#BlueJ package file
dependency1.from=CalcEngineTester
dependency1.to=CalcEngine
dependency1.type=UsesDependency
objectbench.height=76
objectbench.width=700
package.editor.height=435
package.editor.width=592
package.editor.x=70
package.editor.y=80
package.numDependencies=1
package.numTargets=2
package.showExtends=true
package.showUses=true
project.charset=UTF-8
readme.editor.height=515
readme.editor.width=853
readme.editor.x=30
readme.editor.y=23
target1.editor.height=753
target1.editor.width=885
target1.editor.x=50
target1.editor.y=47
target1.height=60
target1.name=CalcEngineTester
target1.naviview.expanded=true
target1.showInterface=false
target1.type=ClassTarget
target1.typeParameters=
target1.width=130
target1.x=130
target1.y=100
target2.editor.height=700
target2.editor.width=900
target2.editor.x=36
target2.editor.y=23
target2.height=60
target2.name=CalcEngine
target2.naviview.expanded=true
target2.showInterface=false
target2.type=ClassTarget
target2.typeParameters=
target2.width=130
target2.x=280
target2.y=200

35
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/CalcEngine.ctxt Executable file
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#BlueJ class context
comment0.params=
comment0.target=CalcEngine()
comment0.text=\n\ Create\ a\ CalcEngine\ instance.\n
comment1.params=
comment1.target=int\ getDisplayValue()
comment1.text=\n\ @return\ The\ value\ currently\ displayed\n\ on\ the\ calculator.\n
comment10.params=
comment10.target=void\ applyPreviousOperator()
comment10.text=\n\ An\ operator\ button\ has\ been\ pressed.\n\ Apply\ the\ immediately\ preceding\ operator\ to\n\ calculate\ an\ intermediate\ result.\ This\ will\n\ form\ the\ left\ operand\ of\ the\ new\ operator.\n
comment2.params=number
comment2.target=void\ numberPressed(int)
comment2.text=\n\ A\ number\ button\ was\ pressed.\n\ @param\ number\ The\ single\ digit.\n
comment3.params=
comment3.target=void\ plus()
comment3.text=\n\ The\ '+'\ button\ was\ pressed.\ \n
comment4.params=
comment4.target=void\ minus()
comment4.text=\n\ The\ '-'\ button\ was\ pressed.\n
comment5.params=
comment5.target=void\ equals()
comment5.text=\n\ The\ '\='\ button\ was\ pressed.\n
comment6.params=
comment6.target=void\ clear()
comment6.text=\n\ The\ 'C'\ (clear)\ button\ was\ pressed.\n
comment7.params=
comment7.target=java.lang.String\ getTitle()
comment7.text=\n\ @return\ The\ title\ of\ this\ calculation\ engine.\n
comment8.params=
comment8.target=java.lang.String\ getAuthor()
comment8.text=\n\ @return\ The\ author\ of\ this\ engine.\n
comment9.params=
comment9.target=java.lang.String\ getVersion()
comment9.text=\n\ @return\ The\ version\ number\ of\ this\ engine.\n
numComments=11

129
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/CalcEngine.java Executable file
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/**
* The main part of the calculator performing the
* arithmetic logic of the calculations.
* @author Hacker T. Largebrain
* @version 1.0
*/
public class CalcEngine
{
// The value in the display.
private int displayValue;
// The previous operator typed (+ or -).
private char previousOperator;
// The left operand to previousOperator.
private int leftOperand;
/**
* Create a CalcEngine instance.
*/
public CalcEngine()
{
displayValue = 0;
previousOperator = ' ';
leftOperand = 0;
}
/**
* @return The value currently displayed
* on the calculator.
*/
public int getDisplayValue()
{
return displayValue;
}
/**
* A number button was pressed.
* @param number The single digit.
*/
public void numberPressed(int number)
{
displayValue = displayValue * 10 + number;
}
/**
* The '+' button was pressed.
*/
public void plus()
{
applyPreviousOperator();
previousOperator = '+';
displayValue = 0;
}
/**
* The '-' button was pressed.
*/
public void minus()
{
applyPreviousOperator();
previousOperator = '-';
displayValue = 0;
}
/**
* The '=' button was pressed.
*/
public void equals()
{
if(previousOperator == '+') {
displayValue = leftOperand + displayValue;
}
else {
displayValue = leftOperand - displayValue;
}
leftOperand = 0;
}
/**
* The 'C' (clear) button was pressed.
*/
public void clear()
{
displayValue = 0;
}
/**
* @return The title of this calculation engine.
*/
public String getTitle()
{
return "Super Calculator";
}
/**
* @return The author of this engine.
*/
public String getAuthor()
{
return "Hacker T. Largebrain";
}
/**
* @return The version number of this engine.
*/
public String getVersion()
{
return "version 0.2";
}
/**
* An operator button has been pressed.
* Apply the immediately preceding operator to
* calculate an intermediate result. This will
* form the left operand of the new operator.
*/
private void applyPreviousOperator()
{
if(previousOperator == '+') {
leftOperand += displayValue;
}
else if(previousOperator == '-') {
leftOperand -= displayValue;
}
else {
// There was no preceding operator.
leftOperand = displayValue;
}
}
}

14
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/CalcEngineTester.ctxt Executable file
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#BlueJ class context
comment0.params=
comment0.target=CalcEngineTester()
comment0.text=\n\ Constructor\ for\ objects\ of\ class\ CalcEngineTester\n
comment1.params=
comment1.target=void\ testAll()
comment1.text=\n\ Test\ everything.\n
comment2.params=
comment2.target=int\ testPlus()
comment2.text=\n\ Test\ the\ plus\ operation\ of\ the\ engine.\n\ @return\ the\ result\ of\ calculating\ 3+4.\n
comment3.params=
comment3.target=int\ testMinus()
comment3.text=\n\ Test\ the\ minus\ operation\ of\ the\ engine.\n\ @return\ the\ result\ of\ calculating\ 9\ -\ 4.\n
numComments=4

65
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/CalcEngineTester.java Executable file
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/**
* Test the CalcEngine class.
*
* @author Hacker T. Largebrain
* @version 1.0
*/
public class CalcEngineTester
{
// The engine to be tested.
private CalcEngine engine;
/**
* Constructor for objects of class CalcEngineTester
*/
public CalcEngineTester()
{
engine = new CalcEngine();
}
/**
* Test everything.
*/
public void testAll()
{
System.out.println("Testing the addition operation.");
System.out.println("The result is: " + testPlus());
System.out.println("Testing the subtraction operation.");
System.out.println("The result is: " + testMinus());
System.out.println("All tests passed.");
}
/**
* Test the plus operation of the engine.
* @return the result of calculating 3+4.
*/
public int testPlus()
{
// Make sure the engine is in a valid starting state.
engine.clear();
// Simulate the key presses: 3 + 4 =
engine.numberPressed(3);
engine.plus();
engine.numberPressed(4);
engine.equals();
// Return the result, which should be 7.
return engine.getDisplayValue();
}
/**
* Test the minus operation of the engine.
* @return the result of calculating 9 - 4.
*/
public int testMinus()
{
// Make sure the engine is in a valid starting state.
engine.clear();
// Simulate the presses: 9 - 4 =
engine.numberPressed(9);
engine.minus();
engine.numberPressed(4);
engine.equals();
// Return the result, which should be 5.
return engine.getDisplayValue();
}
}

8
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/README.TXT Executable file
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------------------------------------------------------------------------
Super Calculator
Author: Hacker T. Largebrain
------------------------------------------------------------------------
This program implements a highly efficient calculating engine for
a pocket calculator. It includes a complete test rig to demonstrate
that the engine works as it should.

45
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/package.bluej Executable file
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#BlueJ package file
dependency1.from=CalcEngineTester
dependency1.to=CalcEngine
dependency1.type=UsesDependency
objectbench.height=76
objectbench.width=694
package.editor.height=435
package.editor.width=586
package.editor.x=70
package.editor.y=80
package.numDependencies=1
package.numTargets=2
package.showExtends=true
package.showUses=true
project.charset=UTF-8
readme.editor.height=564
readme.editor.width=861
readme.editor.x=33
readme.editor.y=23
target1.editor.height=706
target1.editor.width=884
target1.editor.x=36
target1.editor.y=55
target1.height=60
target1.name=CalcEngineTester
target1.naviview.expanded=true
target1.showInterface=false
target1.type=ClassTarget
target1.typeParameters=
target1.width=130
target1.x=140
target1.y=80
target2.editor.height=722
target2.editor.width=904
target2.editor.x=47
target2.editor.y=30
target2.height=60
target2.name=CalcEngine
target2.naviview.expanded=true
target2.showInterface=false
target2.type=ClassTarget
target2.typeParameters=
target2.width=130
target2.x=300
target2.y=180

41
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-full-solution/CalcEngine.ctxt Executable file
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#BlueJ class context
comment0.params=
comment0.target=CalcEngine()
comment0.text=\n\ Create\ a\ CalcEngine.\n
comment1.params=
comment1.target=int\ getDisplayValue()
comment1.text=\n\ @return\ The\ value\ that\ should\ currently\ be\ displayed\n\ on\ the\ calculator\ display.\n
comment10.params=
comment10.target=void\ calculateResult()
comment10.text=\n\ Combine\ leftOperand,\ lastOperator,\ and\ the\n\ current\ display\ value.\n\ The\ result\ becomes\ both\ the\ leftOperand\ and\n\ the\ new\ display\ value.\n
comment11.params=operator
comment11.target=void\ applyOperator(char)
comment11.text=\n\ Apply\ an\ operator.\n\ @param\ operator\ The\ operator\ to\ apply.\n
comment12.params=
comment12.target=void\ keySequenceError()
comment12.text=\n\ Report\ an\ error\ in\ the\ sequence\ of\ keys\ that\ was\ pressed.\n
comment2.params=number
comment2.target=void\ numberPressed(int)
comment2.text=\n\ A\ number\ button\ was\ pressed.\n\ Either\ start\ a\ new\ operand,\ or\ incorporate\ this\ number\ as\n\ the\ least\ significant\ digit\ of\ an\ existing\ one.\n\ @param\ number\ The\ number\ pressed\ on\ the\ calculator.\n
comment3.params=
comment3.target=void\ plus()
comment3.text=\n\ The\ 'plus'\ button\ was\ pressed.\ \n
comment4.params=
comment4.target=void\ minus()
comment4.text=\n\ The\ 'minus'\ button\ was\ pressed.\n
comment5.params=
comment5.target=void\ equals()
comment5.text=\n\ The\ '\='\ button\ was\ pressed.\n
comment6.params=
comment6.target=void\ clear()
comment6.text=\n\ The\ 'C'\ (clear)\ button\ was\ pressed.\n\ Reset\ everything\ to\ a\ starting\ state.\n
comment7.params=
comment7.target=java.lang.String\ getTitle()
comment7.text=\n\ @return\ The\ title\ of\ this\ calculation\ engine.\n
comment8.params=
comment8.target=java.lang.String\ getAuthor()
comment8.text=\n\ @return\ The\ author\ of\ this\ engine.\n
comment9.params=
comment9.target=java.lang.String\ getVersion()
comment9.text=\n\ @return\ The\ version\ number\ of\ this\ engine.\n
numComments=13

196
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-full-solution/CalcEngine.java Executable file
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/**
* The main part of the calculator doing the calculations.
*
* @author David J. Barnes and Michael Kölling
* @version 2016.02.29
*/
public class CalcEngine
{
// The calculator's state is maintained in three fields:
// buildingDisplayValue, haveLeftOperand, and lastOperator.
// Are we already building a value in the display, or will the
// next digit be the first of a new one?
private boolean buildingDisplayValue;
// Has a left operand already been entered (or calculated)?
private boolean haveLeftOperand;
// The most recent operator that was entered.
private char lastOperator;
// The current value (to be) shown in the display.
private int displayValue;
// The value of an existing left operand.
private int leftOperand;
/**
* Create a CalcEngine.
*/
public CalcEngine()
{
clear();
}
/**
* @return The value that should currently be displayed
* on the calculator display.
*/
public int getDisplayValue()
{
return displayValue;
}
/**
* A number button was pressed.
* Either start a new operand, or incorporate this number as
* the least significant digit of an existing one.
* @param number The number pressed on the calculator.
*/
public void numberPressed(int number)
{
if(buildingDisplayValue) {
// Incorporate this digit.
displayValue = displayValue*10 + number;
}
else {
// Start building a new number.
displayValue = number;
buildingDisplayValue = true;
}
}
/**
* The 'plus' button was pressed.
*/
public void plus()
{
applyOperator('+');
}
/**
* The 'minus' button was pressed.
*/
public void minus()
{
applyOperator('-');
}
/**
* The '=' button was pressed.
*/
public void equals()
{
// This should completes the building of a second operand,
// so ensure that we really have a left operand, an operator
// and a right operand.
if(haveLeftOperand &&
lastOperator != '?' &&
buildingDisplayValue) {
calculateResult();
lastOperator = '?';
buildingDisplayValue = false;
}
else {
keySequenceError();
}
}
/**
* The 'C' (clear) button was pressed.
* Reset everything to a starting state.
*/
public void clear()
{
lastOperator = '?';
haveLeftOperand = false;
buildingDisplayValue = false;
displayValue = 0;
}
/**
* @return The title of this calculation engine.
*/
public String getTitle()
{
return "Java Calculator";
}
/**
* @return The author of this engine.
*/
public String getAuthor()
{
return "David J. Barnes and Michael Kölling";
}
/**
* @return The version number of this engine.
*/
public String getVersion()
{
return "Version 1.0";
}
/**
* Combine leftOperand, lastOperator, and the
* current display value.
* The result becomes both the leftOperand and
* the new display value.
*/
private void calculateResult()
{
switch(lastOperator) {
case '+':
displayValue = leftOperand + displayValue;
haveLeftOperand = true;
leftOperand = displayValue;
break;
case '-':
displayValue = leftOperand - displayValue;
haveLeftOperand = true;
leftOperand = displayValue;
break;
default:
keySequenceError();
break;
}
}
/**
* Apply an operator.
* @param operator The operator to apply.
*/
private void applyOperator(char operator)
{
// If we are not in the process of building a new operand
// then it is an error, unless we have just calculated a
// result using '='.
if(!buildingDisplayValue &&
!(haveLeftOperand && lastOperator == '?')) {
keySequenceError();
return;
}
if(lastOperator != '?') {
// First apply the previous operator.
calculateResult();
}
else {
// The displayValue now becomes the left operand of this
// new operator.
haveLeftOperand = true;
leftOperand = displayValue;
}
lastOperator = operator;
buildingDisplayValue = false;
}
/**
* Report an error in the sequence of keys that was pressed.
*/
private void keySequenceError()
{
System.out.println("A key sequence error has occurred.");
// Reset everything.
clear();
}
}

8
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-full-solution/Calculator.ctxt Executable file
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#BlueJ class context
comment0.params=
comment0.target=Calculator()
comment0.text=\n\ Create\ a\ new\ calculator\ and\ show\ it.\n
comment1.params=
comment1.target=void\ show()
comment1.text=\n\ In\ case\ the\ window\ was\ closed,\ show\ it\ again.\n
numComments=2

29
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-full-solution/Calculator.java Executable file
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/**
* The main class of a simple calculator. Create one of these and you'll
* get the calculator on screen.
*
* @author: Michael Kölling and David J. Barnes
* @version 2016.02.29
*/
public class Calculator
{
private CalcEngine engine;
private UserInterface gui;
/**
* Create a new calculator and show it.
*/
public Calculator()
{
engine = new CalcEngine();
gui = new UserInterface(engine);
}
/**
* In case the window was closed, show it again.
*/
public void show()
{
gui.setVisible(true);
}
}

14
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-full-solution/README.TXT Executable file
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Project: calculator-full-solution
Authors: Michael Kölling and David J. Barnes
This project is part of the material for the book
Objects First with Java - A Practical Introduction using BlueJ
Sixth edition
David J. Barnes and Michael Kölling
Pearson Education, 2016
This version of the project implements a complete
solution to the simple calculator discussed in
Chapter 9.

23
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-full-solution/UserInterface.ctxt Executable file
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#BlueJ class context
comment0.params=engine
comment0.target=UserInterface(CalcEngine)
comment0.text=\n\ Create\ a\ user\ interface.\n\ @param\ engine\ The\ calculator\ engine.\n
comment1.params=visible
comment1.target=void\ setVisible(boolean)
comment1.text=\n\ Set\ the\ visibility\ of\ the\ interface.\n\ @param\ visible\ true\ if\ the\ interface\ is\ to\ be\ made\ visible,\ false\ otherwise.\n
comment2.params=
comment2.target=void\ makeFrame()
comment2.text=\n\ Make\ the\ frame\ for\ the\ user\ interface.\n
comment3.params=panel\ buttonText\ action
comment3.target=void\ addButton(java.awt.Container,\ java.lang.String,\ UserInterface.ButtonAction)
comment3.text=\n\ Add\ a\ button\ to\ the\ button\ panel.\n\ @param\ panel\ The\ panel\ to\ receive\ the\ button.\n\ @param\ buttonText\ The\ text\ for\ the\ button.\n\ @param\ action\ Action\ to\ be\ taken\ by\ the\ button.\n
comment4.params=panel\ digit
comment4.target=void\ addNumberButton(java.awt.Container,\ int)
comment4.text=\n\ Add\ a\ number\ button\ to\ the\ button\ panel.\n\ @param\ panel\ The\ panel\ to\ receive\ the\ button.\n\ @param\ digit\ The\ single\ digit\ on\ the\ button.\n
comment5.params=
comment5.target=void\ redisplay()
comment5.text=\n\ Update\ the\ interface\ display\ to\ show\ the\ current\ value\ of\ the\ \n\ calculator.\n
comment6.params=
comment6.target=void\ showInfo()
comment6.text=\n\ Toggle\ the\ info\ display\ in\ the\ calculator's\ status\ area\ between\ the\n\ author\ and\ version\ information.\n
numComments=7

144
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-full-solution/UserInterface.java Executable file
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import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
/**
* A graphical user interface for the calculator. No calculation is being
* done here. This class is responsible just for putting up the display on
* screen. It then refers to the "CalcEngine" to do all the real work.
*
* @author: Michael Kölling and David J. Barnes
* @version 2016.02.29
*/
public class UserInterface
{
private CalcEngine calc;
private boolean showingAuthor;
private JFrame frame;
private JTextField display;
private JLabel status;
/**
* Create a user interface.
* @param engine The calculator engine.
*/
public UserInterface(CalcEngine engine)
{
calc = engine;
showingAuthor = true;
makeFrame();
frame.setVisible(true);
}
/**
* Set the visibility of the interface.
* @param visible true if the interface is to be made visible, false otherwise.
*/
public void setVisible(boolean visible)
{
frame.setVisible(visible);
}
/**
* Make the frame for the user interface.
*/
private void makeFrame()
{
frame = new JFrame(calc.getTitle());
JPanel contentPane = (JPanel)frame.getContentPane();
contentPane.setLayout(new BorderLayout(8, 8));
contentPane.setBorder(new EmptyBorder( 10, 10, 10, 10));
display = new JTextField();
contentPane.add(display, BorderLayout.NORTH);
JPanel buttonPanel = new JPanel(new GridLayout(4, 4));
addNumberButton(buttonPanel, 7);
addNumberButton(buttonPanel, 8);
addNumberButton(buttonPanel, 9);
addButton(buttonPanel, "C", () -> calc.clear());
addNumberButton(buttonPanel, 4);
addNumberButton(buttonPanel, 5);
addNumberButton(buttonPanel, 6);
addButton(buttonPanel, "?", () -> showInfo());
addNumberButton(buttonPanel, 1);
addNumberButton(buttonPanel, 2);
addNumberButton(buttonPanel, 3);
buttonPanel.add(new JLabel(" "));
addNumberButton(buttonPanel, 0);
addButton(buttonPanel, "+", () -> calc.plus());
addButton(buttonPanel, "-", () -> calc.minus());
addButton(buttonPanel, "=", () -> calc.equals());
contentPane.add(buttonPanel, BorderLayout.CENTER);
status = new JLabel(calc.getAuthor());
contentPane.add(status, BorderLayout.SOUTH);
frame.pack();
}
/**
* Add a button to the button panel.
* @param panel The panel to receive the button.
* @param buttonText The text for the button.
* @param action Action to be taken by the button.
*/
private void addButton(Container panel, String buttonText, ButtonAction action)
{
JButton button = new JButton(buttonText);
button.addActionListener(e -> { action.act(); redisplay(); });
panel.add(button);
}
/**
* Add a number button to the button panel.
* @param panel The panel to receive the button.
* @param digit The single digit on the button.
*/
private void addNumberButton(Container panel, int digit)
{
addButton(panel, "" + digit, () -> calc.numberPressed(digit));
}
/**
* Update the interface display to show the current value of the
* calculator.
*/
private void redisplay()
{
display.setText("" + calc.getDisplayValue());
}
/**
* Toggle the info display in the calculator's status area between the
* author and version information.
*/
private void showInfo()
{
if(showingAuthor)
status.setText(calc.getVersion());
else
status.setText(calc.getAuthor());
showingAuthor = !showingAuthor;
}
/**
* Functional interface for button actions.
*/
@FunctionalInterface
private interface ButtonAction
{
/**
* Act on a button press.
*/
public void act();
}
}

64
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-full-solution/package.bluej Executable file
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#BlueJ package file
dependency1.from=UserInterface
dependency1.to=CalcEngine
dependency1.type=UsesDependency
dependency2.from=Calculator
dependency2.to=CalcEngine
dependency2.type=UsesDependency
dependency3.from=Calculator
dependency3.to=UserInterface
dependency3.type=UsesDependency
objectbench.height=76
objectbench.width=775
package.editor.height=435
package.editor.width=667
package.editor.x=70
package.editor.y=80
package.numDependencies=3
package.numTargets=3
package.showExtends=true
package.showUses=true
project.charset=UTF-8
readme.editor.height=521
readme.editor.width=840
readme.editor.x=30
readme.editor.y=23
target1.editor.height=723
target1.editor.width=824
target1.editor.x=50
target1.editor.y=60
target1.height=60
target1.name=Calculator
target1.naviview.expanded=true
target1.showInterface=false
target1.type=ClassTarget
target1.typeParameters=
target1.width=140
target1.x=110
target1.y=80
target2.editor.height=664
target2.editor.width=848
target2.editor.x=37
target2.editor.y=23
target2.height=60
target2.name=UserInterface
target2.naviview.expanded=true
target2.showInterface=false
target2.type=ClassTarget
target2.typeParameters=
target2.width=140
target2.x=280
target2.y=170
target3.editor.height=732
target3.editor.width=681
target3.editor.x=103
target3.editor.y=39
target3.height=60
target3.name=CalcEngine
target3.naviview.expanded=false
target3.showInterface=false
target3.type=ClassTarget
target3.typeParameters=
target3.width=140
target3.x=450
target3.y=260

32
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-gui/CalcEngine.ctxt Executable file
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#BlueJ class context
comment0.params=
comment0.target=CalcEngine()
comment0.text=\n\ Create\ a\ CalcEngine.\n
comment1.params=
comment1.target=int\ getDisplayValue()
comment1.text=\n\ @return\ The\ value\ that\ should\ currently\ be\ displayed\n\ on\ the\ calculator\ display.\n
comment2.params=number
comment2.target=void\ numberPressed(int)
comment2.text=\n\ A\ number\ button\ was\ pressed.\n\ Either\ start\ a\ new\ operand,\ or\ incorporate\ this\ number\ as\n\ the\ least\ significant\ digit\ of\ an\ existing\ one.\n\ @param\ number\ The\ number\ pressed\ on\ the\ calculator.\n
comment3.params=
comment3.target=void\ plus()
comment3.text=\n\ The\ 'plus'\ button\ was\ pressed.\ \n
comment4.params=
comment4.target=void\ minus()
comment4.text=\n\ The\ 'minus'\ button\ was\ pressed.\n
comment5.params=
comment5.target=void\ equals()
comment5.text=\n\ The\ '\='\ button\ was\ pressed.\n
comment6.params=
comment6.target=void\ clear()
comment6.text=\n\ The\ 'C'\ (clear)\ button\ was\ pressed.\n
comment7.params=
comment7.target=java.lang.String\ getTitle()
comment7.text=\n\ @return\ The\ title\ of\ this\ calculation\ engine.\n
comment8.params=
comment8.target=java.lang.String\ getAuthor()
comment8.text=\n\ @return\ The\ author\ of\ this\ engine.\ This\ string\ is\ displayed\ as\ it\ is,\n\ so\ it\ should\ say\ something\ like\ "Written\ by\ H.\ Simpson".\n
comment9.params=
comment9.target=java.lang.String\ getVersion()
comment9.text=\n\ @return\ The\ version\ number\ of\ this\ engine.\ This\ string\ is\ displayed\ as\ \n\ it\ is,\ so\ it\ should\ say\ something\ like\ "Version\ 1.1".\n
numComments=10

90
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-gui/CalcEngine.java Executable file
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/**
* The main part of the calculator doing the calculations.
*
* @author: (none yet)
* @version 0.1 (incomplete)
*/
public class CalcEngine
{
// Put instance variables here.
/**
* Create a CalcEngine.
*/
public CalcEngine()
{
}
/**
* @return The value that should currently be displayed
* on the calculator display.
*/
public int getDisplayValue()
{
return 0;
}
/**
* A number button was pressed.
* Either start a new operand, or incorporate this number as
* the least significant digit of an existing one.
* @param number The number pressed on the calculator.
*/
public void numberPressed(int number)
{
}
/**
* The 'plus' button was pressed.
*/
public void plus()
{
}
/**
* The 'minus' button was pressed.
*/
public void minus()
{
}
/**
* The '=' button was pressed.
*/
public void equals()
{
}
/**
* The 'C' (clear) button was pressed.
*/
public void clear()
{
}
/**
* @return The title of this calculation engine.
*/
public String getTitle()
{
return "";
}
/**
* @return The author of this engine. This string is displayed as it is,
* so it should say something like "Written by H. Simpson".
*/
public String getAuthor()
{
return "";
}
/**
* @return The version number of this engine. This string is displayed as
* it is, so it should say something like "Version 1.1".
*/
public String getVersion()
{
return "";
}
}

8
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-gui/Calculator.ctxt Executable file
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#BlueJ class context
comment0.params=
comment0.target=Calculator()
comment0.text=\n\ Create\ a\ new\ calculator\ and\ show\ it.\n
comment1.params=
comment1.target=void\ show()
comment1.text=\n\ In\ case\ the\ window\ was\ closed,\ show\ it\ again.\n
numComments=2

30
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-gui/Calculator.java Executable file
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/**
* The main class of a simple calculator. Create one of these and you'll
* get the calculator on screen.
*
* @author: Michael Kölling and David J. Barnes
* @version 2016.02.29
*/
public class Calculator
{
private CalcEngine engine;
private UserInterface gui;
/**
* Create a new calculator and show it.
*/
public Calculator()
{
engine = new CalcEngine();
gui = new UserInterface(engine);
}
/**
* In case the window was closed, show it again.
*/
public void show()
{
gui.setVisible(true);
}
}

21
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-gui/README.TXT Executable file
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Project: calculator-gui
Authors: Michael Kölling and David J. Barnes
This project is part of the material for the book
Objects First with Java - A Practical Introduction using BlueJ
Sixth edition
David J. Barnes and Michael Kölling
Pearson Education, 2016
This program is meant to implement a simple pocket calculator.
In its initial version, it is incomplete.
The Calculator and UserInterface classes can be used as they are, but the
CalcEngine, the bit that does the real calculations, has not been implemented.
It is your task to finish the job. Have fun!
To start this application (once you have implemented the missing bits) just
create an object of class Calculator.

23
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-gui/UserInterface.ctxt Executable file
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@@ -0,0 +1,23 @@
#BlueJ class context
comment0.params=engine
comment0.target=UserInterface(CalcEngine)
comment0.text=\n\ Create\ a\ user\ interface.\n\ @param\ engine\ The\ calculator\ engine.\n
comment1.params=visible
comment1.target=void\ setVisible(boolean)
comment1.text=\n\ Set\ the\ visibility\ of\ the\ interface.\n\ @param\ visible\ true\ if\ the\ interface\ is\ to\ be\ made\ visible,\ false\ otherwise.\n
comment2.params=
comment2.target=void\ makeFrame()
comment2.text=\n\ Make\ the\ frame\ for\ the\ user\ interface.\n
comment3.params=panel\ buttonText\ action
comment3.target=void\ addButton(java.awt.Container,\ java.lang.String,\ UserInterface.ButtonAction)
comment3.text=\n\ Add\ a\ button\ to\ the\ button\ panel.\n\ @param\ panel\ The\ panel\ to\ receive\ the\ button.\n\ @param\ buttonText\ The\ text\ for\ the\ button.\n\ @param\ action\ Action\ to\ be\ taken\ by\ the\ button.\n
comment4.params=panel\ digit
comment4.target=void\ addNumberButton(java.awt.Container,\ int)
comment4.text=\n\ Add\ a\ number\ button\ to\ the\ button\ panel.\n\ @param\ panel\ The\ panel\ to\ receive\ the\ button.\n\ @param\ digit\ The\ single\ digit\ on\ the\ button.\n
comment5.params=
comment5.target=void\ redisplay()
comment5.text=\n\ Update\ the\ interface\ display\ to\ show\ the\ current\ value\ of\ the\ \n\ calculator.\n
comment6.params=
comment6.target=void\ showInfo()
comment6.text=\n\ Toggle\ the\ info\ display\ in\ the\ calculator's\ status\ area\ between\ the\n\ author\ and\ version\ information.\n
numComments=7

144
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-gui/UserInterface.java Executable file
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import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
/**
* A graphical user interface for the calculator. No calculation is being
* done here. This class is responsible just for putting up the display on
* screen. It then refers to the "CalcEngine" to do all the real work.
*
* @author: Michael Kölling and David J. Barnes
* @version 2016.02.29
*/
public class UserInterface
{
private CalcEngine calc;
private boolean showingAuthor;
private JFrame frame;
private JTextField display;
private JLabel status;
/**
* Create a user interface.
* @param engine The calculator engine.
*/
public UserInterface(CalcEngine engine)
{
calc = engine;
showingAuthor = true;
makeFrame();
frame.setVisible(true);
}
/**
* Set the visibility of the interface.
* @param visible true if the interface is to be made visible, false otherwise.
*/
public void setVisible(boolean visible)
{
frame.setVisible(visible);
}
/**
* Make the frame for the user interface.
*/
private void makeFrame()
{
frame = new JFrame(calc.getTitle());
JPanel contentPane = (JPanel)frame.getContentPane();
contentPane.setLayout(new BorderLayout(8, 8));
contentPane.setBorder(new EmptyBorder( 10, 10, 10, 10));
display = new JTextField();
contentPane.add(display, BorderLayout.NORTH);
JPanel buttonPanel = new JPanel(new GridLayout(4, 4));
addNumberButton(buttonPanel, 7);
addNumberButton(buttonPanel, 8);
addNumberButton(buttonPanel, 9);
addButton(buttonPanel, "C", () -> calc.clear());
addNumberButton(buttonPanel, 4);
addNumberButton(buttonPanel, 5);
addNumberButton(buttonPanel, 6);
addButton(buttonPanel, "?", () -> showInfo());
addNumberButton(buttonPanel, 1);
addNumberButton(buttonPanel, 2);
addNumberButton(buttonPanel, 3);
buttonPanel.add(new JLabel(" "));
addNumberButton(buttonPanel, 0);
addButton(buttonPanel, "+", () -> calc.plus());
addButton(buttonPanel, "-", () -> calc.minus());
addButton(buttonPanel, "=", () -> calc.equals());
contentPane.add(buttonPanel, BorderLayout.CENTER);
status = new JLabel(calc.getAuthor());
contentPane.add(status, BorderLayout.SOUTH);
frame.pack();
}
/**
* Add a button to the button panel.
* @param panel The panel to receive the button.
* @param buttonText The text for the button.
* @param action Action to be taken by the button.
*/
private void addButton(Container panel, String buttonText, ButtonAction action)
{
JButton button = new JButton(buttonText);
button.addActionListener(e -> { action.act(); redisplay(); });
panel.add(button);
}
/**
* Add a number button to the button panel.
* @param panel The panel to receive the button.
* @param digit The single digit on the button.
*/
private void addNumberButton(Container panel, int digit)
{
addButton(panel, "" + digit, () -> calc.numberPressed(digit));
}
/**
* Update the interface display to show the current value of the
* calculator.
*/
private void redisplay()
{
display.setText("" + calc.getDisplayValue());
}
/**
* Toggle the info display in the calculator's status area between the
* author and version information.
*/
private void showInfo()
{
if(showingAuthor)
status.setText(calc.getVersion());
else
status.setText(calc.getAuthor());
showingAuthor = !showingAuthor;
}
/**
* Functional interface for button actions.
*/
@FunctionalInterface
private interface ButtonAction
{
/**
* Act on a button press.
*/
public void act();
}
}

64
Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-gui/package.bluej Executable file
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#BlueJ package file
dependency1.from=UserInterface
dependency1.to=CalcEngine
dependency1.type=UsesDependency
dependency2.from=Calculator
dependency2.to=CalcEngine
dependency2.type=UsesDependency
dependency3.from=Calculator
dependency3.to=UserInterface
dependency3.type=UsesDependency
objectbench.height=76
objectbench.width=760
package.editor.height=435
package.editor.width=652
package.editor.x=70
package.editor.y=80
package.numDependencies=3
package.numTargets=3
package.showExtends=true
package.showUses=true
project.charset=UTF-8
readme.editor.height=602
readme.editor.width=814
readme.editor.x=41
readme.editor.y=23
target1.editor.height=735
target1.editor.width=843
target1.editor.x=50
target1.editor.y=60
target1.height=60
target1.name=Calculator
target1.naviview.expanded=true
target1.showInterface=false
target1.type=ClassTarget
target1.typeParameters=
target1.width=100
target1.x=80
target1.y=70
target2.editor.height=696
target2.editor.width=822
target2.editor.x=99
target2.editor.y=49
target2.height=60
target2.name=UserInterface
target2.naviview.expanded=false
target2.showInterface=false
target2.type=ClassTarget
target2.typeParameters=
target2.width=120
target2.x=240
target2.y=150
target3.editor.height=721
target3.editor.width=870
target3.editor.x=50
target3.editor.y=60
target3.height=60
target3.name=CalcEngine
target3.naviview.expanded=true
target3.showInterface=false
target3.type=ClassTarget
target3.typeParameters=
target3.width=120
target3.x=430
target3.y=230

23
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop-junit/Comment.ctxt Executable file
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#BlueJ class context
comment0.params=author\ text\ rating
comment0.target=Comment(java.lang.String,\ java.lang.String,\ int)
comment0.text=\n\ Create\ a\ comment\ with\ all\ necessary\ details.\ The\ initial\ vote\ balance\ is\ 0.\n
comment1.params=
comment1.target=void\ upvote()
comment1.text=\n\ Indicate\ that\ this\ comment\ is\ useful\ ('upvote').\ This\ is\ used\ when\ a\ reader\ clicks\n\ the\ 'Yes'\ button\ after\ the\ "Was\ this\ comment\ helpful?"\ quesion.\n
comment2.params=
comment2.target=void\ downvote()
comment2.text=\n\ Indicate\ that\ this\ comment\ is\ not\ useful\ ('downvote').\ This\ is\ used\ when\ a\ reader\n\ clicks\ the\ 'No'\ button\ after\ the\ "Was\ this\ comment\ helpful?"\ quesion.\n
comment3.params=
comment3.target=java.lang.String\ getAuthor()
comment3.text=\n\ Return\ the\ author\ of\ this\ comment.\n
comment4.params=
comment4.target=int\ getRating()
comment4.text=\n\ Return\ the\ rating\ of\ this\ comment.\n
comment5.params=
comment5.target=int\ getVoteCount()
comment5.text=\n\ Return\ the\ vote\ count\ (balance\ of\ up\ and\ down-votes).\n
comment6.params=
comment6.target=java.lang.String\ getFullDetails()
comment6.text=\n\ Return\ the\ full\ text\ and\ details\ of\ the\ comment,\ including\ \n\ the\ comment\ text,\ author\ and\ rating.\n
numComments=7

87
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop-junit/Comment.java Executable file
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/**
* This class represents a comment left for a sales item on an online sales site.
* A comment consists of a comment text, a rating, and an author name. Other users
* can indicate whether the comment was useful or not (called 'upvoting' or
* 'downvoting'). The balance between upvotes and downvotes is stored with comments.
* A negative vote balance means that the comment received more downvotes than upvotes.
*
* @author Michael Kölling and David J. Barnes
* @version 2016.02.29
*/
public class Comment
{
private String author;
private String text;
private int rating;
private int votes;
/**
* Create a comment with all necessary details. The initial vote balance is 0.
*/
public Comment(String author, String text, int rating)
{
this.author = author;
this.text = text;
this.rating = rating;
votes = 0;
}
/**
* Indicate that this comment is useful ('upvote'). This is used when a reader clicks
* the 'Yes' button after the "Was this comment helpful?" quesion.
*/
public void upvote()
{
votes++;
}
/**
* Indicate that this comment is not useful ('downvote'). This is used when a reader
* clicks the 'No' button after the "Was this comment helpful?" quesion.
*/
public void downvote()
{
votes--;
}
/**
* Return the author of this comment.
*/
public String getAuthor()
{
return author;
}
/**
* Return the rating of this comment.
*/
public int getRating()
{
return rating;
}
/**
* Return the vote count (balance of up and down-votes).
*/
public int getVoteCount()
{
return votes;
}
/**
* Return the full text and details of the comment, including
* the comment text, author and rating.
*/
public String getFullDetails()
{
String details = "Rating: " + "*****".substring(0,rating) + " "
+ "By: " + author + "\n"
+ " " + text + "\n";
// Note: 'votes' is currently included for testing purposes only. In the final
// application, this will nt be shown. Instead, the vote count will be used to
// select and order the comments on screen.
details += "(Voted as helpful: " + votes + ")\n";
return details;
}
}

19
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop-junit/README.TXT Executable file
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Project: online-shop-junit
Authors: Michael Kölling and David J. Barnes
This project is part of the material for the book
Objects First with Java - A Practical Introduction using BlueJ
Sixth edition
David J. Barnes and Michael Kölling
Pearson Education, 2016
This project implements a small part of an online sales system (such as Amazon.com).
The current project is concerned only with customer comments for sales items. It contains
code to create, store, show and manipulate customer comments.
The purpose of this project is to introduce regression testing using JUnit. It includes
a test class that demonstrates some of the testing functionality. Testing is further
discussed in the book.
NOTE: There are several serious errors to be found in these classes.

41
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop-junit/SalesItem.ctxt Executable file
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#BlueJ class context
comment0.params=name\ price
comment0.target=SalesItem(java.lang.String,\ int)
comment0.text=\n\ Create\ a\ new\ sales\ item.\n
comment1.params=
comment1.target=java.lang.String\ getName()
comment1.text=\n\ Return\ the\ name\ of\ this\ item.\n
comment10.params=rating
comment10.target=boolean\ ratingInvalid(int)
comment10.text=\n\ Check\ whether\ the\ given\ rating\ is\ invalid.\ Return\ true\ if\ it\ is\ invalid.\n\ Valid\ ratings\ are\ in\ the\ range\ [1..5].\n
comment11.params=author
comment11.target=Comment\ findCommentByAuthor(java.lang.String)
comment11.text=\n\ Find\ the\ comment\ by\ the\ author\ with\ the\ given\ name.\n\ \n\ @return\ The\ comment\ if\ it\ exists;\ null\ if\ it\ doesn't.\n
comment12.params=price
comment12.target=java.lang.String\ priceString(int)
comment12.text=\n\ For\ a\ price\ given\ as\ an\ int,\ return\ a\ readable\ String\ representing\ the\ same\ price.\n\ The\ price\ is\ given\ in\ whole\ cents.\ For\ example\ for\ price\=\=12345,\ the\ following\ String\n\ is\ returned\:\ $123.45\n
comment2.params=
comment2.target=int\ getPrice()
comment2.text=\n\ Return\ the\ price\ of\ this\ item.\n
comment3.params=
comment3.target=int\ getNumberOfComments()
comment3.text=\n\ Return\ the\ number\ of\ customer\ comments\ for\ this\ item.\n
comment4.params=author\ text\ rating
comment4.target=boolean\ addComment(java.lang.String,\ java.lang.String,\ int)
comment4.text=\n\ Add\ a\ comment\ to\ the\ comment\ list\ of\ this\ sales\ item.\ Return\ true\ if\ successful;\n\ false\ if\ the\ comment\ was\ rejected.\n\ \n\ The\ comment\ will\ be\ rejected\ if\ the\ same\ author\ has\ already\ left\ a\ comment,\ or\n\ if\ the\ rating\ is\ invalid.\ Valid\ ratings\ are\ numbers\ between\ 1\ and\ 5\ (inclusive).\n
comment5.params=index
comment5.target=void\ removeComment(int)
comment5.text=\n\ Remove\ the\ comment\ stored\ at\ the\ index\ given.\ If\ the\ index\ is\ invalid,\ do\ nothing.\n
comment6.params=index
comment6.target=void\ upvoteComment(int)
comment6.text=\n\ Upvote\ the\ comment\ at\ 'index'.\ That\ is\:\ count\ this\ comment\ as\ more\ helpful.\n\ If\ the\ index\ is\ invalid,\ do\ nothing.\n
comment7.params=index
comment7.target=void\ downvoteComment(int)
comment7.text=\n\ Downvote\ the\ comment\ at\ 'index'.\ That\ is\:\ count\ this\ comment\ as\ less\ helpful.\n\ If\ the\ index\ is\ invalid,\ do\ nothing.\n
comment8.params=
comment8.target=void\ showInfo()
comment8.text=\n\ Show\ all\ comments\ on\ screen.\ (Currently,\ for\ testing\ purposes\:\ print\ to\ the\ terminal.\n\ Modify\ later\ for\ web\ display.)\n
comment9.params=
comment9.target=Comment\ findMostHelpfulComment()
comment9.text=\n\ Return\ the\ most\ helpful\ comment.\ The\ most\ useful\ comment\ is\ the\ one\ with\ the\ highest\ vote\n\ balance.\ If\ there\ are\ multiple\ comments\ with\ equal\ highest\ balance,\ return\ any\ one\ of\n\ them.\n
numComments=13

184
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop-junit/SalesItem.java Executable file
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import java.util.ArrayList;
import java.util.Iterator;
/**
* The class represents sales items on an online e-commerce site (such as Amazon.com).
* SalesItem objects store all information relevant to this item, including description,
* price, customer comments, etc.
*
* NOTE: The current version is incomplete! Currently, only code dealing with customer
* comments is here.
*
* @author Michael Kölling and David J. Barnes
* @version 0.1 (2016.02.29)
*/
public class SalesItem
{
private String name;
private int price; // in cents
private ArrayList<Comment> comments;
/**
* Create a new sales item.
*/
public SalesItem(String name, int price)
{
this.name = name;
this.price = price;
comments = new ArrayList<>();
}
/**
* Return the name of this item.
*/
public String getName()
{
return name;
}
/**
* Return the price of this item.
*/
public int getPrice()
{
return price;
}
/**
* Return the number of customer comments for this item.
*/
public int getNumberOfComments()
{
return comments.size();
}
/**
* Add a comment to the comment list of this sales item. Return true if successful;
* false if the comment was rejected.
*
* The comment will be rejected if the same author has already left a comment, or
* if the rating is invalid. Valid ratings are numbers between 1 and 5 (inclusive).
*/
public boolean addComment(String author, String text, int rating)
{
if(ratingInvalid(rating)) { // reject invalid ratings
return false;
}
if(findCommentByAuthor(author) != null) { // reject mutiple comments by same author
return false;
}
comments.add(new Comment(author, text, rating));
return true;
}
/**
* Remove the comment stored at the index given. If the index is invalid, do nothing.
*/
public void removeComment(int index)
{
if(index >=0 && index < comments.size()) { // if index is valid
comments.remove(index);
}
}
/**
* Upvote the comment at 'index'. That is: count this comment as more helpful.
* If the index is invalid, do nothing.
*/
public void upvoteComment(int index)
{
if(index >=0 && index < comments.size()) { // if index is valid
comments.get(index).upvote();
}
}
/**
* Downvote the comment at 'index'. That is: count this comment as less helpful.
* If the index is invalid, do nothing.
*/
public void downvoteComment(int index)
{
if(index >=0 && index < comments.size()) { // if index is valid
comments.get(index).downvote();
}
}
/**
* Show all comments on screen. (Currently, for testing purposes: print to the terminal.
* Modify later for web display.)
*/
public void showInfo()
{
System.out.println("*** " + name + " ***");
System.out.println("Price: " + priceString(price));
System.out.println();
System.out.println("Customer comments:");
for(Comment comment : comments) {
System.out.println("-------------------------------------------");
System.out.println(comment.getFullDetails());
}
System.out.println();
System.out.println("===========================================");
}
/**
* Return the most helpful comment. The most useful comment is the one with the highest vote
* balance. If there are multiple comments with equal highest balance, return any one of
* them.
*/
public Comment findMostHelpfulComment()
{
Iterator<Comment> it = comments.iterator();
Comment best = it.next();
while(it.hasNext()) {
Comment current = it.next();
if(current.getVoteCount() > best.getVoteCount()) {
best = current;
}
}
return best;
}
/**
* Check whether the given rating is invalid. Return true if it is invalid.
* Valid ratings are in the range [1..5].
*/
private boolean ratingInvalid(int rating)
{
return rating < 0 || rating > 5;
}
/**
* Find the comment by the author with the given name.
*
* @return The comment if it exists; null if it doesn't.
*/
private Comment findCommentByAuthor(String author)
{
for(Comment comment : comments) {
if(comment.getAuthor().equals(author)) {
return comment;
}
}
return null;
}
/**
* For a price given as an int, return a readable String representing the same price.
* The price is given in whole cents. For example for price==12345, the following String
* is returned: $123.45
*/
private String priceString(int price)
{
int dollars = price / 100;
int cents = price - (dollars*100);
if(cents <= 9) {
return "$" + dollars + ".0" + cents; // include zero padding if necessary
}
else {
return "$" + dollars + "." + cents;
}
}
}

22
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop-junit/SalesItemTest.ctxt Executable file
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#BlueJ class context
comment0.params=
comment0.target=SalesItemTest()
comment0.text=\n\ Default\ constructor\ for\ test\ class\ SalesItemTest\n
comment1.params=
comment1.target=void\ setUp()
comment1.text=\n\ Sets\ up\ the\ test\ fixture.\n\n\ Called\ before\ every\ test\ case\ method.\n
comment2.params=
comment2.target=void\ tearDown()
comment2.text=\n\ Tears\ down\ the\ test\ fixture.\n\n\ Called\ after\ every\ test\ case\ method.\n
comment3.params=
comment3.target=void\ testAddComment()
comment3.text=\n\ Test\ that\ a\ comment\ can\ be\ added,\ and\ that\ the\ comment\ count\ is\ correct\ afterwards.\n
comment4.params=
comment4.target=void\ testIllegalRating()
comment4.text=\n\ Test\ that\ a\ comment\ using\ an\ illegal\ rating\ value\ is\ rejected.\n
comment5.params=
comment5.target=void\ testInit()
comment5.text=\n\ Test\ that\ a\ sales\ item\ is\ correctly\ initialised\ (name\ and\ price).\n
comment6.params=
comment6.target=void\ addComment()
numComments=7

82
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop-junit/SalesItemTest.java Executable file
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import static org.junit.Assert.*;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
/**
* The test class SalesItemTest.
*
* @author mik
* @version 0.1
*/
public class SalesItemTest
{
/**
* Default constructor for test class SalesItemTest
*/
public SalesItemTest()
{
}
/**
* Sets up the test fixture.
*
* Called before every test case method.
*/
@Before
public void setUp()
{
}
/**
* Tears down the test fixture.
*
* Called after every test case method.
*/
@After
public void tearDown()
{
}
/**
* Test that a comment can be added, and that the comment count is correct afterwards.
*/
@Test
public void testAddComment()
{
SalesItem salesIte1 = new SalesItem("Brain surgery for Dummies", 21998);
assertEquals(true, salesIte1.addComment("James Duckling", "This book is great. I perform brain surgery every week now.", 4));
assertEquals(1, salesIte1.getNumberOfComments());
}
/**
* Test that a comment using an illegal rating value is rejected.
*/
@Test
public void testIllegalRating()
{
SalesItem salesIte1 = new SalesItem("Java For Complete Idiots, Vol 2", 19900);
assertEquals(false, salesIte1.addComment("Joshua Black", "Not worth the money. The font is too small.", -5));
}
/**
* Test that a sales item is correctly initialised (name and price).
*/
@Test
public void testInit()
{
SalesItem salesIte1 = new SalesItem("test name", 1000);
assertEquals("test name", salesIte1.getName());
assertEquals(1000, salesIte1.getPrice());
}
@Test
public void addComment()
{
SalesItem salesIte1 = new SalesItem("Brain Surgery for Dummies.", 9899);
assertEquals(true, salesIte1.addComment("Fred", "Great - I perform brain surgery every week now!", 4));
}
}

59
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop-junit/package.bluej Executable file
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#BlueJ package file
dependency1.from=SalesItem
dependency1.to=Comment
dependency1.type=UsesDependency
objectbench.height=76
objectbench.width=670
package.editor.height=371
package.editor.width=562
package.editor.x=70
package.editor.y=80
package.numDependencies=1
package.numTargets=3
package.showExtends=true
package.showUses=true
project.charset=UTF-8
readme.editor.height=700
readme.editor.width=900
readme.editor.x=50
readme.editor.y=45
target1.editor.height=700
target1.editor.width=921
target1.editor.x=315
target1.editor.y=47
target1.height=60
target1.name=Comment
target1.naviview.expanded=true
target1.showInterface=false
target1.type=ClassTarget
target1.typeParameters=
target1.width=100
target1.x=290
target1.y=210
target2.editor.height=700
target2.editor.width=900
target2.editor.x=100
target2.editor.y=53
target2.height=50
target2.name=SalesItemTest
target2.naviview.expanded=true
target2.showInterface=false
target2.type=UnitTestTargetJunit4
target2.typeParameters=
target2.width=110
target2.x=160
target2.y=70
target3.association=SalesItemTest
target3.editor.height=757
target3.editor.width=967
target3.editor.x=187
target3.editor.y=43
target3.height=60
target3.name=SalesItem
target3.naviview.expanded=true
target3.showInterface=false
target3.type=ClassTarget
target3.typeParameters=
target3.width=110
target3.x=130
target3.y=100

23
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop/Comment.ctxt Executable file
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@@ -0,0 +1,23 @@
#BlueJ class context
comment0.params=author\ text\ rating
comment0.target=Comment(java.lang.String,\ java.lang.String,\ int)
comment0.text=\n\ Create\ a\ comment\ with\ all\ necessary\ details.\ The\ initial\ vote\ balance\ is\ 0.\n
comment1.params=
comment1.target=void\ upvote()
comment1.text=\n\ Indicate\ that\ this\ comment\ is\ useful\ ('upvote').\ This\ is\ used\ when\ a\ reader\ clicks\n\ the\ 'Yes'\ button\ after\ the\ "Was\ this\ comment\ helpful?"\ quesion.\n
comment2.params=
comment2.target=void\ downvote()
comment2.text=\n\ Indicate\ that\ this\ comment\ is\ not\ useful\ ('downvote').\ This\ is\ used\ when\ a\ reader\n\ clicks\ the\ 'No'\ button\ after\ the\ "Was\ this\ comment\ helpful?"\ quesion.\n
comment3.params=
comment3.target=java.lang.String\ getAuthor()
comment3.text=\n\ Return\ the\ author\ of\ this\ comment.\n
comment4.params=
comment4.target=int\ getRating()
comment4.text=\n\ Return\ the\ rating\ of\ this\ comment.\n
comment5.params=
comment5.target=int\ getVoteCount()
comment5.text=\n\ Return\ the\ vote\ count\ (balance\ of\ up\ and\ down-votes).\n
comment6.params=
comment6.target=java.lang.String\ getFullDetails()
comment6.text=\n\ Return\ the\ full\ text\ and\ details\ of\ the\ comment,\ including\ \n\ the\ comment\ text,\ author\ and\ rating.\n
numComments=7

87
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop/Comment.java Executable file
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/**
* This class represents a comment left for a sales item on an online sales site.
* A comment consists of a comment text, a rating, and an author name. Other users
* can indicate whether the comment was useful or not (called 'upvoting' or
* 'downvoting'). The balance between upvotes and downvotes is stored with comments.
* A negative vote balance means that the comment received more downvotes than upvotes.
*
* @author Michael Kölling and David J. Barnes
* @version 2016.02.29
*/
public class Comment
{
private String author;
private String text;
private int rating;
private int votes;
/**
* Create a comment with all necessary details. The initial vote balance is 0.
*/
public Comment(String author, String text, int rating)
{
this.author = author;
this.text = text;
this.rating = rating;
votes = 0;
}
/**
* Indicate that this comment is useful ('upvote'). This is used when a reader clicks
* the 'Yes' button after the "Was this comment helpful?" quesion.
*/
public void upvote()
{
votes++;
}
/**
* Indicate that this comment is not useful ('downvote'). This is used when a reader
* clicks the 'No' button after the "Was this comment helpful?" quesion.
*/
public void downvote()
{
votes--;
}
/**
* Return the author of this comment.
*/
public String getAuthor()
{
return author;
}
/**
* Return the rating of this comment.
*/
public int getRating()
{
return rating;
}
/**
* Return the vote count (balance of up and down-votes).
*/
public int getVoteCount()
{
return votes;
}
/**
* Return the full text and details of the comment, including
* the comment text, author and rating.
*/
public String getFullDetails()
{
String details = "Rating: " + "*****".substring(0,rating) + " "
+ "By: " + author + "\n"
+ " " + text + "\n";
// Note: 'votes' is currently included for testing purposes only. In the final
// application, this will nt be shown. Instead, the vote count will be used to
// select and order the comments on screen.
details += "(Voted as helpful: " + votes + ")\n";
return details;
}
}

15
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop/README.TXT Executable file
View File

@@ -0,0 +1,15 @@
Project: online-shop
Authors: Michael Kölling and David J. Barnes
This project is part of the material for the book
Objects First with Java - A Practical Introduction using BlueJ
Sixth edition
David J. Barnes and Michael Kölling
Pearson Education, 2016
This project implements a small part of an online sales system (such as Amazon.com).
The current project is concerned only with customer comments for sales items. It contains
code to create, store, show and manipulate customer comments.
NOTE: There are several serious errors to be found in these classes.

41
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop/SalesItem.ctxt Executable file
View File

@@ -0,0 +1,41 @@
#BlueJ class context
comment0.params=name\ price
comment0.target=SalesItem(java.lang.String,\ int)
comment0.text=\n\ Create\ a\ new\ sales\ item.\n
comment1.params=
comment1.target=java.lang.String\ getName()
comment1.text=\n\ Return\ the\ name\ of\ this\ item.\n
comment10.params=rating
comment10.target=boolean\ ratingInvalid(int)
comment10.text=\n\ Check\ whether\ the\ given\ rating\ is\ invalid.\ Return\ true\ if\ it\ is\ invalid.\n\ Valid\ ratings\ are\ in\ the\ range\ [1..5].\n
comment11.params=author
comment11.target=Comment\ findCommentByAuthor(java.lang.String)
comment11.text=\n\ Find\ the\ comment\ by\ the\ author\ with\ the\ given\ name.\n\ \n\ @return\ The\ comment\ if\ it\ exists;\ null\ if\ it\ doesn't.\n
comment12.params=price
comment12.target=java.lang.String\ priceString(int)
comment12.text=\n\ For\ a\ price\ given\ as\ an\ int,\ return\ a\ readable\ String\ representing\ the\ same\ price.\n\ The\ price\ is\ given\ in\ whole\ cents.\ For\ example\ for\ price\=\=12345,\ the\ following\ String\n\ is\ returned\:\ $123.45\n
comment2.params=
comment2.target=int\ getPrice()
comment2.text=\n\ Return\ the\ price\ of\ this\ item.\n
comment3.params=
comment3.target=int\ getNumberOfComments()
comment3.text=\n\ Return\ the\ number\ of\ customer\ comments\ for\ this\ item.\n
comment4.params=author\ text\ rating
comment4.target=boolean\ addComment(java.lang.String,\ java.lang.String,\ int)
comment4.text=\n\ Add\ a\ comment\ to\ the\ comment\ list\ of\ this\ sales\ item.\ Return\ true\ if\ successful;\n\ false\ if\ the\ comment\ was\ rejected.\n\ \n\ The\ comment\ will\ be\ rejected\ if\ the\ same\ author\ has\ already\ left\ a\ comment,\ or\n\ if\ the\ rating\ is\ invalid.\ Valid\ ratings\ are\ numbers\ between\ 1\ and\ 5\ (inclusive).\n
comment5.params=index
comment5.target=void\ removeComment(int)
comment5.text=\n\ Remove\ the\ comment\ stored\ at\ the\ index\ given.\ If\ the\ index\ is\ invalid,\ do\ nothing.\n
comment6.params=index
comment6.target=void\ upvoteComment(int)
comment6.text=\n\ Upvote\ the\ comment\ at\ 'index'.\ That\ is\:\ count\ this\ comment\ as\ more\ helpful.\n\ If\ the\ index\ is\ invalid,\ do\ nothing.\n
comment7.params=index
comment7.target=void\ downvoteComment(int)
comment7.text=\n\ Downvote\ the\ comment\ at\ 'index'.\ That\ is\:\ count\ this\ comment\ as\ less\ helpful.\n\ If\ the\ index\ is\ invalid,\ do\ nothing.\n
comment8.params=
comment8.target=void\ showInfo()
comment8.text=\n\ Show\ all\ comments\ on\ screen.\ (Currently,\ for\ testing\ purposes\:\ print\ to\ the\ terminal.\n\ Modify\ later\ for\ web\ display.)\n
comment9.params=
comment9.target=Comment\ findMostHelpfulComment()
comment9.text=\n\ Return\ the\ most\ helpful\ comment.\ The\ most\ useful\ comment\ is\ the\ one\ with\ the\ highest\ vote\n\ balance.\ If\ there\ are\ multiple\ comments\ with\ equal\ highest\ balance,\ return\ any\ one\ of\n\ them.\n
numComments=13

184
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop/SalesItem.java Executable file
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import java.util.ArrayList;
import java.util.Iterator;
/**
* The class represents sales items on an online e-commerce site (such as Amazon.com).
* SalesItem objects store all information relevant to this item, including description,
* price, customer comments, etc.
*
* NOTE: The current version is incomplete! Currently, only code dealing with customer
* comments is here.
*
* @author Michael Kölling and David J. Barnes
* @version 0.1 (2016.02.29)
*/
public class SalesItem
{
private String name;
private int price; // in cents
private ArrayList<Comment> comments;
/**
* Create a new sales item.
*/
public SalesItem(String name, int price)
{
this.name = name;
this.price = price;
comments = new ArrayList<>();
}
/**
* Return the name of this item.
*/
public String getName()
{
return name;
}
/**
* Return the price of this item.
*/
public int getPrice()
{
return price;
}
/**
* Return the number of customer comments for this item.
*/
public int getNumberOfComments()
{
return comments.size();
}
/**
* Add a comment to the comment list of this sales item. Return true if successful;
* false if the comment was rejected.
*
* The comment will be rejected if the same author has already left a comment, or
* if the rating is invalid. Valid ratings are numbers between 1 and 5 (inclusive).
*/
public boolean addComment(String author, String text, int rating)
{
if(ratingInvalid(rating)) { // reject invalid ratings
return false;
}
if(findCommentByAuthor(author) != null) { // reject mutiple comments by same author
return false;
}
comments.add(new Comment(author, text, rating));
return true;
}
/**
* Remove the comment stored at the index given. If the index is invalid, do nothing.
*/
public void removeComment(int index)
{
if(index >=0 && index < comments.size()) { // if index is valid
comments.remove(index);
}
}
/**
* Upvote the comment at 'index'. That is: count this comment as more helpful.
* If the index is invalid, do nothing.
*/
public void upvoteComment(int index)
{
if(index >=0 && index < comments.size()) { // if index is valid
comments.get(index).upvote();
}
}
/**
* Downvote the comment at 'index'. That is: count this comment as less helpful.
* If the index is invalid, do nothing.
*/
public void downvoteComment(int index)
{
if(index >=0 && index < comments.size()) { // if index is valid
comments.get(index).downvote();
}
}
/**
* Show all comments on screen. (Currently, for testing purposes: print to the terminal.
* Modify later for web display.)
*/
public void showInfo()
{
System.out.println("*** " + name + " ***");
System.out.println("Price: " + priceString(price));
System.out.println();
System.out.println("Customer comments:");
for(Comment comment : comments) {
System.out.println("-------------------------------------------");
System.out.println(comment.getFullDetails());
}
System.out.println();
System.out.println("===========================================");
}
/**
* Return the most helpful comment. The most useful comment is the one with the highest vote
* balance. If there are multiple comments with equal highest balance, return any one of
* them.
*/
public Comment findMostHelpfulComment()
{
Iterator<Comment> it = comments.iterator();
Comment best = it.next();
while(it.hasNext()) {
Comment current = it.next();
if(current.getVoteCount() > best.getVoteCount()) {
best = current;
}
}
return best;
}
/**
* Check whether the given rating is invalid. Return true if it is invalid.
* Valid ratings are in the range [1..5].
*/
private boolean ratingInvalid(int rating)
{
return rating < 0 || rating > 5;
}
/**
* Find the comment by the author with the given name.
*
* @return The comment if it exists; null if it doesn't.
*/
private Comment findCommentByAuthor(String author)
{
for(Comment comment : comments) {
if(comment.getAuthor().equals(author)) {
return comment;
}
}
return null;
}
/**
* For a price given as an int, return a readable String representing the same price.
* The price is given in whole cents. For example for price==12345, the following String
* is returned: $123.45
*/
private String priceString(int price)
{
int dollars = price / 100;
int cents = price - (dollars*100);
if(cents <= 9) {
return "$" + dollars + ".0" + cents; // include zero padding if necessary
}
else {
return "$" + dollars + "." + cents;
}
}
}

45
Semester 1/Programming 1/Java/examples/projects/chapter09/online-shop/package.bluej Executable file
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#BlueJ package file
dependency1.from=SalesItem
dependency1.to=Comment
dependency1.type=UsesDependency
objectbench.height=76
objectbench.width=753
package.editor.height=431
package.editor.width=645
package.editor.x=70
package.editor.y=80
package.numDependencies=1
package.numTargets=2
package.showExtends=true
package.showUses=true
project.charset=UTF-8
readme.editor.height=700
readme.editor.width=900
readme.editor.x=53
readme.editor.y=23
target1.editor.height=700
target1.editor.width=921
target1.editor.x=62
target1.editor.y=59
target1.height=60
target1.name=Comment
target1.naviview.expanded=true
target1.showInterface=false
target1.type=ClassTarget
target1.typeParameters=
target1.width=100
target1.x=290
target1.y=210
target2.editor.height=752
target2.editor.width=937
target2.editor.x=53
target2.editor.y=49
target2.height=60
target2.name=SalesItem
target2.naviview.expanded=true
target2.showInterface=false
target2.type=ClassTarget
target2.typeParameters=
target2.width=100
target2.x=160
target2.y=110