很急，麻烦大家来帮我解决一下，谢谢了先！！！

Question

一个java文件里只有一个pbulic类public class Cal extends JFrame  改为：
class Cal extends JFrame我记得大概是这样，具体的你再查查书。

Answer 1

JButton b[] = new JButton[names.length];b[i]=new JButton( names[i] );

Answer 2

JButton b[]没有初始化
...
       c.setLayout(layout);
b = new JButton[names.length];//加上这一句
       for(int i=0;i<names.length;i++){
...

Answer 3

   public static void main(String[] args)
   {
      Cal app=new Cal();
      
      app.addWindowListener(new WindowAdapter(){
          public void windowClosing(WindowEvent e){
             System.exit(0);
          }
       }
    );     <-这里多了一个"；"

Answer 4

//我在修改的地方加了 //**
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;public class Cal extends JFrame{
   private JButton b[];
   private String names[]=
   {"7","8","9","/","4","5","6","*"
,"1","2","3","-","0",".","=","+"};
   private GridLayout layout;
   
   public Cal()
   {
       super("calculator");
       layout=new GridLayout(4,4);
       Container c=getContentPane();
       c.setLayout(layout);
    
   b=new JButton[names.length]; //**
   
       for(int i=0;i<names.length;i++){
            b[i]=new JButton( names[i] );
            c.add(b[i]);
       }
       setSize(300,400);  
       show();
   }    
       
   public static void main(String[] args)
   {
      Cal app=new Cal();
      
      app.addWindowListener(new WindowAdapter(){
          public void windowClosing(WindowEvent e){
             System.exit(0);
          }
       }
    );
  }
}   

Answer 5

谢谢大家了 问题已经解决了 
b=new JButton[names.length]; 这一行如果写成b[]=new JButton[names.length];就不行了 为什么啊 ？？？？ 我申明的是JButton b[];可实例话的时候怎么是
b=new JButton[names.length];？？？？？？？？