java，Swing中单击实现两点相连

这是老师给我们的一个作业，做完了，当做自己的第一篇博文吧。

       程序运行后，弹出黑色界面，有三个白圈，标有北京，上海，广州，点击任意一圈，即出现云另外两全的连线。Java学的不精，之前一直在思考如何实现在已有的图上的线条绘制。后采用八个参数将其解决。

       import java.awt.BasicStroke;import java.awt.BorderLayout;import java.awt.Canvas;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.event.MouseAdapter;import java.awt.event.MouseEvent;import java.awt.event.MouseListener;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JPanel;public class ConnPlace extends JFrame {int x,y,x1,y1,x2,y2,m1,n1,m2,n2;Color col=new Color(200,200,200);private final Font font=new Font("华文琥珀",Font.BOLD,32); JPanel contentPanel=new MyJPanel();BasicStroke pen = new BasicStroke(2.0f, BasicStroke.CAP_BUTT, BasicStroke.JOIN_ROUND); Graphics2D g2=null;public ConnPlace(){super();this.setSize(600, 400);contentPanel.setBackground(new Color(0,0,0));setContentPane(contentPanel);setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);this.setTitle("客运连线实验");addMouseListener(new MouseAdapter() { //继承适配器MouseAdapter，重写单击方法public void mouseClicked(MouseEvent e) { // 发生单击事件时被触发x=e.getX();y=e.getY();if((x-150)*(x-150)+(y-100)*(y-100)<=2500){x1=200;y1=100;m1=400;n1=100;x2=150;y2=150;m2=250;n2=250;}else if((x-450)*(x-450)+(y-100)*(y-100)<=2500){x1=200;y1=100;m1=400;n1=100;x2=450;y2=150;m2=350;n2=250;}else if((x-300)*(x-300)+(y-250)*(y-250)<=2500){x1=150;y1=150;m1=250;n1=250;x2=450;y2=150;m2=350;n2=250;}else{x1=0;y1=0;m1=0;n1=0;x2=0;y2=0;m2=0;n2=0;};contentPanel.repaint();}});}public static void main(String[] args) {new ConnPlace().setVisible(true);}class MyJPanel extends JPanel {public void paint(Graphics g) { super.paint(g); g2 = (Graphics2D)g;g2.setColor(col);g2.setFont(font);g2.setStroke(pen);g2.drawOval(100,50, 100, 100);// 绘制第1个圆形g2.drawOval(400,50, 100, 100);// 绘制第2个圆形g2.drawOval(250,200, 100, 100); // 绘制第3个圆形g2.drawString("北京", 118, 110);g2.drawString("上海", 418, 110);g2.drawString("广州", 268, 260);g2.drawLine(x1,y1,m1,n1);g2.drawLine(x2,y2,m2,n2);} }}