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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();
+    }
+}