Applet Life Cycle

In this article we will learn about applet life cycle and various life cycle methods of an applet along with example program.

The life cycle of an applet is as shown in the figure below:

As shown in the above diagram, the life cycle of an applet starts with init() method and ends with destroy() method. Other life cycle methods are start(), stop() and paint(). The methods to execute only once in the applet life cycle are init() and destroy(). Other methods execute multiple times.

Below is the description of each applet life cycle method:

init(): The init() method is the first method to execute when the applet is executed. Variable declaration and initialization operations are performed in this method.

start(): The start() method contains the actual code of the applet that should run. The start() method executes immediately after the init() method. It also executes whenever the applet is restored, maximized or moving from one tab to another tab in the browser.

stop(): The stop() method stops the execution of the applet. The stop() method executes when the applet is minimized or when moving from one tab to another in the browser.

destroy(): The destroy() method executes when the applet window is closed or when the tab containing the webpage is closed. stop() method executes just before when destroy() method is invoked. The destroy() method removes the applet object from memory.

paint(): The paint() method is used to redraw the output on the applet display area. The paint() method executes after the execution of start() method and whenever the applet or browser is resized.

The method execution sequence when an applet is executed is:

• init()
• start()
• paint()

The method execution sequence when an applet is closed is:

• stop()
• destroy()

Example program that demonstrates the life cycle of an applet is as follows:

import java.awt.*;
import java.applet.*;
public class MyApplet extends Applet 
{
	public void init()
	{
		System.out.println("Applet initialized");
	}
	public void start()
	{
		System.out.println("Applet execution started");
	}
	public void stop()
	{
		System.out.println("Applet execution stopped");
	}
	public void paint(Graphics g)
	{
		System.out.println("Painting...");
	}
	public void destroy()
	{
		System.out.println("Applet destroyed");
	}
}

Output of the above applet program when run using appletviewer tool is:

Applet initialized
Applet execution started
Painting…
Painting…
Applet execution stopped
Applet destroyed