first commit

Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/CalcEngine.ctxt

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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

Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/CalcEngine.java

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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;
+        }
+    }
+}

Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/CalcEngineTester.ctxt

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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

Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/CalcEngineTester.java

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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();
+    }
+}

Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/README.TXT

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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.

Semester 1/Programming 1/Java/examples/projects/chapter09/calculator-engine/package.bluej

@@ -0,0 +1,45 @@
+#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