import java.awt.BorderLayout;import java.awt.Color;import java.awt.Font;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JOptionPane;import javax.swing.JPanel;import javax.swing.JTextField;public class B extends JFrame implements ActionListener{ int max=300; JLabel jlTitle=new JLabel(); JLabel jlTotal=new JLabel("共"+max+"题"); JLabel jl=new JLabel(""); JLabel jlcorrect=new JLabel(); JTextField jtf=new JTextField(3); JButton jb1=new JButton("上一题"); JButton jb2=new JButton("下一题"); JButton jb3=new JButton("交卷"); JPanel jp1=new JPanel(); JPanel jp2=new JPanel(); JPanel jp3=new JPanel(); String[] question=new String[max]; int[] answer=new int[max]; String[] studentAnswer=new String[max]; boolean[]correct=new boolean[max]; int count=1; boolean submitFlag=false; B(){  super("小学算术测试");  jlTitle.setFont(new Font(null,Font.PLAIN,20));  jlTotal.setFont(new Font(null,Font.PLAIN,20));  jl.setFont(new Font(null,Font.PLAIN,20));  jlcorrect.setFont(new Font(null,Font.PLAIN,20));  jlcorrect.setForeground(Color.RED);  jtf.setFont(new Font(null,Font.PLAIN,20));  for(int i=0;i
     
      MAX||answer<0){   int a=(int)(Math.random()*MAX+1);   int b=(int)(Math.random()*MAX+1);   int c=(int)(Math.random()*4+1);   switch(c){    case 1:answer=a+b;break;    case 2:answer=a-b;break;    case 3:answer=a*b;break;    case 4:     if(a%b==0){      answer=a/b;     }     break;   }   if(answer<=MAX&&answer>=0){    s=s+a;    switch(c){     case 1:s=s+"+";break;     case 2:s=s+"-";break;     case 3:s=s+"*";break;     case 4:s=s+"/";break;    }    s=s+b+"="+answer;   }  }  return s; }}