Functions and Arrays
Digital Clocks, HTML Page Parameters - Con't
This advanced digital clock uses GIF digits to display the time. Also we implemented blinking dots, to make it even prettier. To tell which digit GIFs we have to draw, we pass a substring from the string, containing hour, minute or second to a little method which draws the correct digit in the right position for us. Always try to split your code into as many logical functions (methods) as possible!
If you would like to further explore the time and date functions of Java, take a look at the API documentation or the following little demo program. The last line (weekday) makes use of a switch statement. This is often used as a shorter replacement for many if/else statements. In the brackets you put the variable (must be of type integer, short or char) which is tested in the branches of the body. Since the function getDay() returns a number in the range 0 to 6, we have to somehow convert it into the name of the corresponding weekday, so the switch statement comes in handy.
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//Sourcecode
import java.awt.*;
import java.applet.*;
//we need to import the util package for the time functions
import java.util.*;
public class Project21 extends Applet implements Runnable
{
Thread runner;
Image Buffer;
Graphics gBuffer;
public void init()
{
//create off-screen image we can draw to
Buffer=createImage(size().width,size().height);
gBuffer=Buffer.getGraphics();
}
public void start()
{
if (runner == null)
{
runner = new Thread (this);
runner.start();
}
}
public void stop()
{
if (runner != null)
{
runner.stop();
runner = null;
}
}
public void run()
{
while(true)
{
//halt the thread for 100 ms here
try {runner.sleep(100);}
catch (Exception e) { }
repaint();
}
}
public void update(Graphics g)
{
paint(g);
}
public void paint (Graphics g)
{
//create a new time object
Date today=new Date();
//repaint the background green
gBuffer.setColor(Color.green);
gBuffer.fillRect(0,0,size().width,size().height);
//set a new font we create "on the fly"
gBuffer.setFont(new Font("Helvetica", Font.PLAIN,16));
gBuffer.setColor(Color.black);
gBuffer.drawString("toGMTString(): "+today.toGMTString(),20,20);
gBuffer.drawString("toLocaleString(): "+today.toLocaleString(),20,40);
gBuffer.drawString("toString(): "+today.toString(),20,60);
gBuffer.drawString("getYear(): "+today.getYear(),20,80);
gBuffer.drawString("getMonth(): "+today.getMonth(),20,100);
gBuffer.drawString("getDate(): "+today.getDate(),20,120);
gBuffer.drawString("getHours(): "+today.getHours(),20,140);
gBuffer.drawString("getMinutes(): "+today.getMinutes(),20,160);
gBuffer.drawString("getSeconds(): "+today.getSeconds(),20,180);
gBuffer.drawString("getDay(): "+today.getDay(),20,200);
switch(today.getDay())
{
case 0: gBuffer.drawString("Today is Sunday",20,240);
break;
case 1: gBuffer.drawString("Today is Monday",20,240);
break;
case 2: gBuffer.drawString("Today is Tuesday",20,240);
break;
case 3: gBuffer.drawString("Today is Wednesday",20,240);
break;
case 4: gBuffer.drawString("Today is Thursday",20,240);
break;
case 5: gBuffer.drawString("Today is Friday",20,240);
break;
case 6: gBuffer.drawString("Today is Saturday",20,240);
break;
}
//copy the buffer to the screen (no flickering!)
g.drawImage (Buffer,0,0, this);
}
}
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