Inter-Applet communication across different pages

import java.applet.*;    
import java.awt.*;
import java.awt.event.*;
import java.net.*;

public class FirstAppletJ extends Applet implements
    ActionListener {
 Button b;
 TextField t;
 public void init() {
  add(new Label("Message to 2nd applet :"));
  add(t= new TextField(20));
  add(b = new Button("Load 2nd applet"));
  b.addActionListener(this);
  }

 public void actionPerformed(ActionEvent ae) {
  if (ae.getSource() == b) {
    try {
     getAppletContext().showDocument
       (new URL(getCodeBase(), 
         "SecondAppletJ.html?" + "message=" 
              + URLEncoder.encode(t.getText())));
     }
    catch (Exception e) {
     e.printStackTrace();
     }
    } 
   }
}

<HTML><HEAD></HEAD><BODY>
<APPLET CODE="SecondAppletJ.class" 
        HEIGHT=100 
        WIDTH=400>
</APPLET></BODY></HTML>

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

public class SecondAppletJ extends Applet {
 public void init() {
   Label l = new Label("Message from 1st Applet");
   add (l);
   TextField tf = new TextField( 50 );
   add(tf);
   
   // complete current URL
   String s = getDocumentBase().toString();
   
   // extract the search (or query) section
   String theMessage = s.substring(s.indexOf('?') + 1);

   // remove message header
   theMessage = theMessage.substring("message=".length());

   // decode the string (incomplete)
   theMessage = theMessage.replace('+',' ');

   /* 
        with JDK1.2, the decoding can be done 
        with java.net.URLDecoder.decode(theMessage).
   
      you to convert from a MIME format called "x-www-form-urlencoded" 
      to a String
      To convert to a String, each character is examined in turn:
      . The ASCII characters 'a' through 'z',
        'A' through 'Z', and '0'
        through '9' remain the same.
      . The plus sign '+' is converted into a
        space character ' '.
      . The remaining characters are represented by 3-character
        strings which begin with the percent sign,
        "%xy", where xy is the two-digit hexadecimal 
        representation of the lower 8-bits of the character.
   */


   
   tf.setText(theMessage);
   }
}

If you need to pass the message via the PARAM tag of the SecondApplet then take a look at this How-to.

Send a message from an Applet to another Applet on a different page