Applet Communication

Applet communication refers to the process of exchanging data or information between two or more applets running in the same or different web pages.

Applets are small programs that are embedded in web pages and are executed within the web browser. They can be used to provide interactive features such as animations, games, and interactive forms.

Applets can communicate with each other using different techniques such as:

1. Shared Variables: Applets can share data by using shared variables that are stored in a common location accessible to both applets. This can be achieved by defining a shared static variable in one applet and accessing it from the other applet.
2. JavaScript Calls: Applets can communicate with each other using JavaScript. One applet can call a JavaScript function defined in the other applet to pass data.
3. Applet-to-Applet Communication Interface (AACI): AACI is a mechanism that allows applets to communicate with each other using a standard interface. The interface defines methods for sending and receiving messages between applets.
4. Remote Method Invocation (RMI): RMI is a Java technology that allows applets to invoke methods on objects running on remote systems. This can be used to exchange data between applets running on different web pages.

Applet communication can be useful in many scenarios such as creating collaborative applications, sharing data between different components of a web page, and integrating multiple applets to provide a more powerful user experience.

Example of Applet Communication:

Here’s an example of how two applets can communicate with each other using shared variables:

Applet 1:

import java.applet.*;
import java.awt.*;

public class Applet1 extends Applet {
    public static int sharedVariable = 0;
    
    public void init() {
        // increment the shared variable every second
        Thread thread = new Thread(() -> {
            while (true) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                sharedVariable++;
                repaint();
            }
        });
        thread.start();
    }
    
    public void paint(Graphics g) {
        g.drawString("Shared variable: " + sharedVariable, 20, 20);
    }
}

Applet 2:

import java.applet.*;
import java.awt.*;

public class Applet2 extends Applet {
    public void init() {
        // access the shared variable every 2 seconds
        Thread thread = new Thread(() -> {
            while (true) {
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                int sharedVariable = Applet1.sharedVariable;
                System.out.println("Shared variable: " + sharedVariable);
            }
        });
        thread.start();
    }
}

In this example, Applet1 defines a static variable called sharedVariable and increments it every second in a separate thread. The value of sharedVariable is displayed in the applet using the paint() method.

Applet2 accesses the sharedVariable every 2 seconds in a separate thread and prints its value to the console using System.out.println().

Both applets are embedded in the same web page and are executed within the same web browser. As a result, Applet2 can access the value of sharedVariable defined in Applet1 and display it in the console.