冒泡排序的动画显示

自己写的一个动画：显示冒泡排序

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.Timer;
import java.util.*;
public class SortAnimation extends JFrame{
    JLabel jlbTitle = new JLabel("Selection Sort");
    SelectionSort selectionsort;
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int num[] = {10,4,7,2,3,8,1,9,5,6};
        SortAnimation frame = new SortAnimation(num);
        frame.setTitle("SortAnimation");
        frame.setSize(300,300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
    public SortAnimation(){
        
    }
    public SortAnimation(int num[]){
        setLayout(new BorderLayout());
        add(jlbTitle, BorderLayout.NORTH);
        selectionsort = new SelectionSort(num);
        add(selectionsort, BorderLayout.CENTER);
    }
    class SelectionSort extends JPanel{
        private int num[];
        private int interval = 10;
        private  int i = 0;
        private  int j = 0;
        public SelectionSort(int num[]){
            this.num = num;
            Timer timer = new Timer(1000, new TimerListener());//每隔一秒进行一次排序
            timer.start();
        }
        public SelectionSort(){
            
        }
        public void setNum(int num[]){
            this.num = num;
            repaint();
        }
        public void sort(){//冒泡排序,每次只排序一次
            if(i < num.length ){
                if(j < num.length - i -1){
                    int temp;
                    if(num[j] > num[j+1]){//将最大的往下沉
                        temp = num[j];
                        num[j] = num[j+1];
                        num[j+1] = temp;
                    }
                    setNum(num);
                    j++;
                }
                    else if(j == num.length - i -1){
                        j=0;
                        i++;
                    }
            }
        }
        protected void paintComponent(Graphics g){
            super.paintComponent(g);
            int width = getWidth();
            int height = getHeight();
            int interval = 10;
            int x[] = {0, 0, interval, interval};
            int y[] = {height, 0, 0, height};
            
            for(int i = 0; i < num.length; i++)
            {
                x[0] = i * 2 * interval;
                x[1] = i * 2 * interval;
                x[2] = (i * 2 + 1)* interval;
                x[3] = (i * 2 + 1)* interval;
                        
                y[1] = height - num[i] * 10;
                y[2] = height - num[i] * 10;
                g.drawPolyline(x, y, 4);
            }
        }
        class TimerListener implements ActionListener{
            public void actionPerformed(ActionEvent e){
                sort();
            }
        }
    }
}