import java.awt.*;
import javax.swing.*;
public class A8_10 extends JFrame{
JMenuBar mb;
JMenu m1,m2;
JMenuItem mt1,mt2;
JTextArea t;
JScrollPane s;
public static void main(String[] args){
A8_10 AA=new A8_10();
}
public A8_10(){
mb=new JMenuBar();
m1=new JMenu("文件（F）");
m1.setMnemonic('F');
m2=new JMenu("编辑（E）");
m2.setMnemonic('E');
mt1=new JMenuItem("打开");
mt1=new JMenuItem("保存");
t=new JTextArea();
s=new JScrollPane(t);
m1.add(mt1);m1.add(mt2);
mb.add(m1);mb.add(m2);
this.setJMenuBar(mb);
this.add(s);
this.setTitle("记事本");
this.setSize(400, 400);
this.setLocation(100,200);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setResizable(false);
this.setVisible(true);
}
}
报错：
Exception in thread "main" java.lang.NullPointerException
at java.awt.Container.addImpl(Container.java:1090)
at java.awt.Container.add(Container.java:410)
at javax.swing.JPopupMenu.add(JPopupMenu.java:290)
at javax.swing.JMenu.add(JMenu.java:579)
at A8_10.<init>(A8_10.java:29)
at A8_10.main(A8_10.java:15)