threadexample.java

window下使用j2ee的jms工具做的网络应用的一个架构程序

/*
Threads are needed when you want to perfom actions over and over again.
We want to show the current time and update that every second.
*/


import java.awt.*;
import java.applet.*;
// We need Date to get the current time.
import java.util.Date;

// Implement Runnable, this will make it possible for threads
// to call the run method when activated.
public class ThreadExample extends Applet implements Runnable
{
	// Define your thread.
	Thread clockThread;
	// This textfield will show the time.
	TextField clockField;
	// Date will give us the current hours, minutes and seconds
	Date date;
	// This variable will remain true for as long
	// we want the thread to run.
	boolean running = true;
	
	public void init()
	{
		// a standard layout to place just one textfield
		setLayout(new BorderLayout());
		
		clockField = new TextField();
		add(clockField,"Center");
		// Create the thread.
		clockThread= new Thread(this);
		// and let it start running
		clockThread.start();
	}
	
	// Very important. You do not want your thread to keep running when
	// the applet is deactivated (eg. user left page)
	public void destroy()
	{
		// will cause thread to stop looping
		running = false;
		// destroy it.
		clockThread = null;
	}
	
	
	// The method that will be called when you have a thread.
	// You always need this when you implement Runnable (use a thread)
	public void run()
	{
		// loop until told to stop
		while (running)
		{
			// Construct the current date.
			date = new Date();
			// Get the hours, minutes and hours
			String time = date.getHours()+":"+date.getMinutes()+":"+date.getSeconds();
			// Put that result in the textfield
			clockField.setText(time);
			//Now the reason for threads
			try
			{
				// Wait 500milliseconds before continuing
				clockThread.sleep(500);
			}
			catch (InterruptedException e)
			{
				System.out.println(e);
			}
			// he has wait and will now restart his actions.
		}
	}
}	
	
/*
Be cautious when using threads, make sure to end them sometime and not to let them run too
fast. When threads are used to time on-screen drawing things could slow down
heavily.
*/