button2.java

java程序设计 清华出版社 孙燮华老师编写的程序源代码

//button2.java, p.55
//revised by X.H.Sun

import java.awt.*;
import java.awt.event.*;

public class button2 extends Frame implements ActionListener{
  TextField text1;
  Button button1,button2;
  String string1;

  public button2(){
  	setLayout(new FlowLayout());
    text1=new TextField(20);
    add(text1);
    button1=new Button("Welcome to ");
    add(button1);
    button1.addActionListener(this);
    button2=new Button("Java");
    add(button2);
    button2.addActionListener(this);
    setSize(200,100);
    setVisible(true);
  }

  public void actionPerformed(ActionEvent e){
    string1="Welcome to";
    if(e.getSource()==button1){
      text1.setText("Welcome to");
    }
    if(e.getSource()==button2){
//  以下相当于append功能, 因TextField类无append(String)方法
//      if(string1.equals(text1.getText())==true)//OK!
      if((text1.getText()).equals(string1)==true)//OK!
        text1.setText(text1.getText()+" Java!"); //
      else
        text1.setText("Java!");
    }
  }
  public static void main(String[] args){
  	new button2();
  }
}