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Semester 1/Programming 1/Java/examples/projects/chapter03/clock-display/ClockDisplay.ctxt

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+#BlueJ class context
+comment0.params=
+comment0.target=ClockDisplay()
+comment0.text=\n\ Constructor\ for\ ClockDisplay\ objects.\ This\ constructor\ \n\ creates\ a\ new\ clock\ set\ at\ 00\:00.\n
+comment1.params=hour\ minute
+comment1.target=ClockDisplay(int,\ int)
+comment1.text=\n\ Constructor\ for\ ClockDisplay\ objects.\ This\ constructor\n\ creates\ a\ new\ clock\ set\ at\ the\ time\ specified\ by\ the\ \n\ parameters.\n
+comment2.params=
+comment2.target=void\ timeTick()
+comment2.text=\n\ This\ method\ should\ get\ called\ once\ every\ minute\ -\ it\ makes\n\ the\ clock\ display\ go\ one\ minute\ forward.\n
+comment3.params=hour\ minute
+comment3.target=void\ setTime(int,\ int)
+comment3.text=\n\ Set\ the\ time\ of\ the\ display\ to\ the\ specified\ hour\ and\n\ minute.\n
+comment4.params=
+comment4.target=java.lang.String\ getTime()
+comment4.text=\n\ Return\ the\ current\ time\ of\ this\ display\ in\ the\ format\ HH\:MM.\n
+comment5.params=
+comment5.target=void\ updateDisplay()
+comment5.text=\n\ Update\ the\ internal\ string\ that\ represents\ the\ display.\n
+numComments=6

Semester 1/Programming 1/Java/examples/projects/chapter03/clock-display/ClockDisplay.java

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+
+/**
+ * The ClockDisplay class implements a digital clock display for a
+ * European-style 24 hour clock. The clock shows hours and minutes. The 
+ * range of the clock is 00:00 (midnight) to 23:59 (one minute before 
+ * midnight).
+ * 
+ * The clock display receives "ticks" (via the timeTick method) every minute
+ * and reacts by incrementing the display. This is done in the usual clock
+ * fashion: the hour increments when the minutes roll over to zero.
+ * 
+ * @author Michael Kölling and David J. Barnes
+ * @version 2016.02.29
+ */
+public class ClockDisplay
+{
+    private NumberDisplay hours;
+    private NumberDisplay minutes;
+    private String displayString;    // simulates the actual display
+    
+    /**
+     * Constructor for ClockDisplay objects. This constructor 
+     * creates a new clock set at 00:00.
+     */
+    public ClockDisplay()
+    {
+        hours = new NumberDisplay(24);
+        minutes = new NumberDisplay(60);
+        updateDisplay();
+    }
+
+    /**
+     * Constructor for ClockDisplay objects. This constructor
+     * creates a new clock set at the time specified by the 
+     * parameters.
+     */
+    public ClockDisplay(int hour, int minute)
+    {
+        hours = new NumberDisplay(24);
+        minutes = new NumberDisplay(60);
+        setTime(hour, minute);
+    }
+
+    /**
+     * This method should get called once every minute - it makes
+     * the clock display go one minute forward.
+     */
+    public void timeTick()
+    {
+        minutes.increment();
+        if(minutes.getValue() == 0) {  // it just rolled over!
+            hours.increment();
+        }
+        updateDisplay();
+    }
+
+    /**
+     * Set the time of the display to the specified hour and
+     * minute.
+     */
+    public void setTime(int hour, int minute)
+    {
+        hours.setValue(hour);
+        minutes.setValue(minute);
+        updateDisplay();
+    }
+
+    /**
+     * Return the current time of this display in the format HH:MM.
+     */
+    public String getTime()
+    {
+        return displayString;
+    }
+    
+    /**
+     * Update the internal string that represents the display.
+     */
+    private void updateDisplay()
+    {
+        displayString = hours.getDisplayValue() + ":" + 
+                        minutes.getDisplayValue();
+    }
+}

Semester 1/Programming 1/Java/examples/projects/chapter03/clock-display/NumberDisplay.ctxt

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+#BlueJ class context
+comment0.params=rollOverLimit
+comment0.target=NumberDisplay(int)
+comment0.text=\n\ Constructor\ for\ objects\ of\ class\ NumberDisplay.\n\ Set\ the\ limit\ at\ which\ the\ display\ rolls\ over.\n
+comment1.params=
+comment1.target=int\ getValue()
+comment1.text=\n\ Return\ the\ current\ value.\n
+comment2.params=
+comment2.target=java.lang.String\ getDisplayValue()
+comment2.text=\n\ Return\ the\ display\ value\ (that\ is,\ the\ current\ value\ as\ a\ two-digit\n\ String.\ If\ the\ value\ is\ less\ than\ ten,\ it\ will\ be\ padded\ with\ a\ leading\n\ zero).\n
+comment3.params=replacementValue
+comment3.target=void\ setValue(int)
+comment3.text=\n\ Set\ the\ value\ of\ the\ display\ to\ the\ new\ specified\ value.\ If\ the\ new\n\ value\ is\ less\ than\ zero\ or\ over\ the\ limit,\ do\ nothing.\n
+comment4.params=
+comment4.target=void\ increment()
+comment4.text=\n\ Increment\ the\ display\ value\ by\ one,\ rolling\ over\ to\ zero\ if\ the\n\ limit\ is\ reached.\n
+numComments=5

Semester 1/Programming 1/Java/examples/projects/chapter03/clock-display/NumberDisplay.java

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+
+/**
+ * The NumberDisplay class represents a digital number display that can hold
+ * values from zero to a given limit. The limit can be specified when creating
+ * the display. The values range from zero (inclusive) to limit-1. If used,
+ * for example, for the seconds on a digital clock, the limit would be 60, 
+ * resulting in display values from 0 to 59. When incremented, the display 
+ * automatically rolls over to zero when reaching the limit.
+ * 
+ * @author Michael Kölling and David J. Barnes
+ * @version 2016.02.29
+ */
+public class NumberDisplay
+{
+    private int limit;
+    private int value;
+
+    /**
+     * Constructor for objects of class NumberDisplay.
+     * Set the limit at which the display rolls over.
+     */
+    public NumberDisplay(int rollOverLimit)
+    {
+        limit = rollOverLimit;
+        value = 0;
+    }
+
+    /**
+     * Return the current value.
+     */
+    public int getValue()
+    {
+        return value;
+    }
+
+    /**
+     * Return the display value (that is, the current value as a two-digit
+     * String. If the value is less than ten, it will be padded with a leading
+     * zero).
+     */
+    public String getDisplayValue()
+    {
+        if(value < 10) {
+            return "0" + value;
+        }
+        else {
+            return "" + value;
+        }
+    }
+
+    /**
+     * Set the value of the display to the new specified value. If the new
+     * value is less than zero or over the limit, do nothing.
+     */
+    public void setValue(int replacementValue)
+    {
+        if((replacementValue >= 0) && (replacementValue < limit)) {
+            value = replacementValue;
+        }
+    }
+
+    /**
+     * Increment the display value by one, rolling over to zero if the
+     * limit is reached.
+     */
+    public void increment()
+    {
+        value = (value + 1) % limit;
+    }
+}

Semester 1/Programming 1/Java/examples/projects/chapter03/clock-display/README.TXT

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+Project: clock-display
+Authors: David Barnes and Michael Kölling
+
+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
+
+It is discussed in chapter 3.
+
+To use this project, create an instance of class ClockDisplay. Then inspect this 
+instance and leave the object inspector window open. With the inspector window open, 
+call the object's methods, such as timeTick and setTime. Watch the 
+"displayString" in the inspector.
+
+The displayString field simulates the actual clock display device. Were this 
+program running in a real clock, it would change the real, physical display 
+hardware instead of this string. The timeTick method would be triggered once 
+every minute by some timer hardware.
+
+Everything else could be pretty much the same.
+
+
+Note: This project does not implement adequate handling of errors.

Semester 1/Programming 1/Java/examples/projects/chapter03/clock-display/package.bluej

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+#BlueJ package file
+dependency1.from=ClockDisplay
+dependency1.to=NumberDisplay
+dependency1.type=UsesDependency
+objectbench.height=124
+objectbench.width=774
+package.editor.height=371
+package.editor.width=666
+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=626
+readme.editor.width=875
+readme.editor.x=53
+readme.editor.y=28
+target1.editor.height=745
+target1.editor.width=845
+target1.editor.x=81
+target1.editor.y=119
+target1.height=60
+target1.name=ClockDisplay
+target1.naviview.expanded=true
+target1.showInterface=false
+target1.type=ClassTarget
+target1.typeParameters=
+target1.width=110
+target1.x=150
+target1.y=100
+target2.editor.height=792
+target2.editor.width=873
+target2.editor.x=97
+target2.editor.y=188
+target2.height=60
+target2.name=NumberDisplay
+target2.naviview.expanded=true
+target2.showInterface=false
+target2.type=ClassTarget
+target2.typeParameters=
+target2.width=110
+target2.x=290
+target2.y=180