2-1
public class HelloJava {
	public static void main(String[ ] args) {
		System.out.println("Hello Java!");
	}
}


2-2
public class A {
	public static void main(String[] args) {
		System.out.println("ϰ");
	}
}

class B{	
}




2-3 HelloWorld.java

import  java.awt.*;
import  java.awt.event.*;
public class HelloWorld {
	public   static   void   main  (String  args[])
	{
		new  FrameInOut();
	}
}
class  FrameInOut   extends  Frame  implements   ActionListener
{
	Label  prompt;
	TextField   input   , output;
	FrameInOut()
	{
		super("java  application");
		prompt= new Label("please  enter  your  name :");
		input= new TextField(6);
		output= new TextField(20);
		setLayout(new  FlowLayout());
		add(prompt);
		add(input);
		add(output);
		input.addActionListener(this);
		setSize(300,200);
	      show();
	}
	public  void  actionPerformed(ActionEvent  e)
	{
		output.setText(input.getText()+",WELCOME");
	}
}
