sender.java

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import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.util.Enumeration;

public class Sender extends Applet 
                    implements ActionListener {
    private String myName;
    private TextField nameField;
    private TextArea status;
    private TextArea statusAnswer;

    public void init() {
        
        setLayout(new GridLayout(4,1));
        Panel p = new Panel();

        Label receiverLabel = new Label("Receiver name:"  );
        p.add(receiverLabel);

        nameField = new TextField(10);
        p.add(nameField);
        nameField.addActionListener(this);

        Button button = new Button("Send message");
        
        p.add(button);
        button.addActionListener(this);

		add(p);

        status = new TextArea(5, 60); //显示applet发送状态。
        status.setEditable(false);
        add(status);
        
        statusAnswer = new TextArea(5, 60);  //显示从receiver接收到的信息。
        statusAnswer.setEditable(false);
		add(statusAnswer);
		
        myName = getParameter("NAME");  //获取applet自身的名字并显示。
        Label senderLabel = new Label("(My name is " + myName + ".)" );
        
        add(senderLabel);


    }

    public void actionPerformed(ActionEvent event) {
        Applet receiver = null;
        String receiverName = nameField.getText(); //Get name to 
                                                   //search for.
        receiver = getAppletContext().getApplet(receiverName);
        if (receiver != null) {
            //Use the instanceof operator to make sure the applet
            //we found is a Receiver object.
            if (!(receiver instanceof Receiver)) {
                status.append("Found applet named " + receiverName + ", "   
                              + "but it's not a Receiver object.\n" );
            } else {
                status.append("Found applet named "
                              + receiverName + "  Sending message to it.\n" );
                          ((Receiver)receiver).processRequestFrom(myName);
            }
        } else {
            status.append("Couldn't find any applet named " + receiverName + "." );
        }
    }

    public void receiveAnswer( String answer){
    	
    	statusAnswer.append("The receiver answer: "+answer+'\n');
    	repaint();
    }
    	 

    public void paint(Graphics g) {
        g.drawRect(0, 0,getSize().width - 1, getSize().height - 1);
    }


}