throwdemo.java

刘艺编著的java教程的课本习题加例题代码 很有用哦！

package ex6_4_1;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;

public class ThrowDemo extends JApplet{
  JTextField tf1=new JTextField("try to use throw",50);
  JTextField tf2=new JTextField("this will not show on the screen");
  //Initialize the applet
  public void init(){
    try{
     Container cp=new Container();
     cp=this.getContentPane();
     cp.setLayout(new BorderLayout());
     cp.add(tf1,BorderLayout.NORTH);
     demo();          //此方法中人为抛出异常，同样具有终止程序执行的功能
     cp.add(tf2);       //cp.add(tf2)将不再被执行
    }
    catch(NullPointerException e){  //捕获demo()抛出的NullPointerException
          tf1.setText("catch an exception: "+e);
    }
  }
  void demo(){
   throw new NullPointerException("this exception is thrown by init");
  }
}