起因：
很久之前就想做做这类的小程序练手，现在才开始动工哈哈哈。
从最简单的开始做起，这次是一个交通灯。
实现了交通灯的简单显示转换循环功能。
基于 java.swing 。
先上效果图。超级超级超级简陋哈哈哈
红灯 黄灯 绿灯
上代码
1 import java.awt.Color; 2 import java.awt.Font; 3 import java.awt.Graphics; 4 import java.util.Timer; 5 import java.util.TimerTask; 6 7 import javax.swing.JFrame; 8 import javax.swing.JLabel; 9 import javax.swing.JPanel; 10 11 /** 12 * @ClassName: TrafficLights 13 * @Description: 实现简单的交通灯转换功能 14 * @author Arrack 15 * @date 2018年1月30日 上午9:49:54 16 * 17 */ 18 public class TrafficLights extends JPanel { 19 /* 20 * serialVersionUID 21 * 相当于java类的身份证。主要用于版本控制。 22 * serialVersionUID作用是序列化时保持版本的兼容性, 23 * 即在版本升级时反序列化仍保持对象的唯一性。 24 * 摘自百度知道 https://zhidao.baidu.com/question/321447087.html 25 */ 26 private static final long serialVersionUID = 1L; 27 28 /* 29 * 定义一系列静态常量 30 * 程序窗口宽度高度，三种颜色亮灯，为空（都熄灭） 31 */ 32 private static final int winWidth = 500; 33 private static final int winHeight = 300; 34 private static final int BLANK = 0; 35 private static final int RED = 1; 36 private static final int YELLOW = 2; 37 private static final int GREEN = 3; 38 39 private static int color = BLANK; // 将初始状态设置为都熄灭状态 40 41 /* 42 * 计算灯的位置和大小（仅与窗口高度和宽度有关） 43 * ps：绘制椭圆时，drawOval(int x, int y, int width, int height) 44 * x,y 为椭圆外接矩形左上顶点的坐标,width,height为矩形两边长。 45 */ 46 private int ballWidth = winHeight / 3; 47 private int ballX = winWidth / 2 - ballWidth / 2 - winWidth / 50, 48 ballY = winHeight / 2 - ballWidth + winHeight / 15; 49 private int ballPadding = (winWidth - 3 * ballWidth) / 4; 50 private int yellowX = ballX; 51 private int redX = ballX - ballPadding - ballWidth; 52 private int greenX = ballX + ballPadding + ballWidth; 53 54 /* 55 * Label 倒计时指示 56 */ 57 private JLabel l = new JLabel(""); 58 59 public TrafficLights() { 60 l.setFont(new Font("Arial", Font.BOLD, 20)); 61 add(l); 62 } 63 64 /** 65 * @Title: changeLights 66 * @Description: 利用timer类，进行灯的变换和闪烁，并显示倒计时 67 * @param @param timeR 红灯持续时间 单位秒 68 * @param @param timeY 黄灯持续时间 69 * @param @param timeG 绿灯持续时间 70 * @return void 71 */ 72 public void changeLights(final int timeR, final int timeY, final int timeG) { 73 final Timer timer = new Timer(); 74 final int num = timeR + timeG + timeY; 75 timer.schedule(new TimerTask() { 76 int i = 1; 77 78 public void run() { 79 i %= num; 80 if (i > 0 && i <= timeR) { // 红灯的时间，红灯持续亮 81 color = RED; 82 l.setText(Integer.toString(timeR + 1 - i)); 83 } else if (i > timeR && i <= timeR + timeY) { // 黄灯的时间，黄灯闪烁，0.6s闪一次 84 color = YELLOW; 85 l.setText(Integer.toString(timeY + 1 86 - (i % timeY != 0 ? i % timeY : timeY))); 87 timer.schedule(new TimerTask() { 88 public void run() { 89 color = BLANK; 90 repaint(); 91 } 92 }, 600); 93 } else { // 绿灯的时间，持续亮 94 color = GREEN; 95 l.setText(Integer.toString(timeG + 1 96 - (i % timeG != 0 ? i % timeG : timeG))); 97 } 98 repaint(); 99 i++;100 }101 }, 0, 1000);102 103 }104 105 /*106 * Title: paintComponent107 * Description: 重写绘制内容函数，利用switch选取显示内容（遮挡方式）108 * @param g 109 * @see javax.swing.JComponent#paintComponent(java.awt.Graphics) 110 */111 protected void paintComponent(Graphics g) {112 113 super.paintComponent(g);114 115 g.setColor(Color.RED);116 g.fillOval(redX, ballY, ballWidth, ballWidth);117 g.setColor(Color.YELLOW);118 g.fillOval(yellowX, ballY, ballWidth, ballWidth);119 g.setColor(Color.GREEN);120 g.fillOval(greenX, ballY, ballWidth, ballWidth);121 g.setColor(this.getBackground());122 switch (color) {123 case RED:124 g.fillRect(yellowX, ballY, greenX - yellowX + ballWidth, ballWidth);125 g.setColor(Color.BLACK);126 g.drawOval(yellowX, ballY, ballWidth, ballWidth);127 g.drawOval(greenX, ballY, ballWidth, ballWidth);128 break;129 case YELLOW:130 g.fillRect(redX, ballY, ballWidth, ballWidth);131 g.fillRect(greenX, ballY, ballWidth, ballWidth);132 g.setColor(Color.BLACK);133 g.drawOval(redX, ballY, ballWidth, ballWidth);134 g.drawOval(greenX, ballY, ballWidth, ballWidth);135 break;136 case GREEN:137 g.fillRect(redX, ballY, yellowX - redX + ballWidth, ballWidth);138 g.setColor(Color.BLACK);139 g.drawOval(redX, ballY, ballWidth, ballWidth);140 g.drawOval(yellowX, ballY, ballWidth, ballWidth);141 break;142 case BLANK:143 g.fillRect(redX, ballY, greenX - redX + ballWidth, ballWidth);144 g.setColor(Color.BLACK);145 g.drawOval(redX, ballY, ballWidth, ballWidth);146 g.drawOval(yellowX, ballY, ballWidth, ballWidth);147 g.drawOval(greenX, ballY, ballWidth, ballWidth);148 default:149 break;150 }151 }152 153 public static void main(String[] args) {154 JPanel p = new TrafficLights();155 JFrame frame = new JFrame("交通灯");156 frame.getContentPane().add(p);157 frame.setSize(winWidth, winHeight);158 frame.setLocation(500, 200);159 frame.setVisible(true);160 frame.setResizable(false);161 ((TrafficLights) p).changeLights(5, 5, 5);162 }163 }