抽签程序Java重置版

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
public class Main{
    public static int StringToInt(String s){
        if (s.length()==0){
            return -1;
        }
        for (int i=0;i<s.length();i++){
            if (!Character.isDigit(s.charAt(i))){
                return -1;
            }
        }
        return Integer.valueOf(s);
    }
    public static void deal(int a,int b){
        if (a<1||b<1||a>1000000||b>100000||a<b){
            JFrame error=new JFrame("ERROR");
            JPanel resu=new JPanel();
            JLabel err=new JLabel("Should check something!");
            err.setForeground(Color.red);
            err.setFont(new Font("黑体",Font.BOLD,24));
            resu.add(err);
            error.add(resu);
            error.setSize(400,80);
            error.setVisible(true);
        }
        else{
            ArrayList<Integer> l=new ArrayList<Integer>();
            String[] r=new String[b];
            JFrame result=new JFrame("Result");
            for (int i=1;i<=a;i++){
                l.add(i);
            }
            for (int i=0;i<b;i++){
                int x=(int)(l.size()*Math.random());
                r[i]=String.valueOf(l.get(x));
                l.remove(x);
            }
            JPanel res=new JPanel();
            JList list=new JList(r);
            list.setVisibleRowCount(20);
            list.setFixedCellWidth(200);
            res.add(new JScrollPane(list));
            result.getContentPane().add(BorderLayout.CENTER,res);
            result.setSize(250,420);
            result.setVisible(true);
        }
    }
    public static void main(String[] args){
        JFrame input=new JFrame("Input");
        JTextField total=new JTextField();
        JTextField participation=new JTextField();
        JButton button=new JButton("OK");
        input.setDefaultCloseOperation(input.EXIT_ON_CLOSE);
        input.addWindowListener(new WindowAdapter(){
            public void actionPerformed(WindowEvent w){
                System.exit(0);
            }
        });
        button.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e){
                int a=StringToInt(total.getText());
                int b=StringToInt(participation.getText());
                deal(a,b);
            }
        });
        JPanel label=new JPanel();
        label.setLayout(new BoxLayout(label,BoxLayout.Y_AXIS));
        JPanel text=new JPanel();
        text.setLayout(new BoxLayout(text,BoxLayout.Y_AXIS));
        label.add(new JLabel("Total:"));
        label.add(new JLabel("Participation:"));
        text.add(total);
        text.add(participation);
        input.getContentPane().add(BorderLayout.WEST,label);
        input.getContentPane().add(BorderLayout.CENTER,text);
        input.getContentPane().add(BorderLayout.SOUTH,button);
        input.setSize(300,100);
        input.setVisible(true);
    }
}