利用线程休眠和Graphics 对象在窗体中画线段，颜色随机产生

package threadTest;
import java.awt.*;
import javax.swing.*;
import java.util.Random;

public class SleepThreadTest extends JFrame{
/**
*
*/
private static final long serialVersionUID = 1L;
private Thread t;
//创建颜色数组
private static Color[] color = {Color.BLACK,Color.BLUE,Color.CYAN,Color.DARK_GRAY,Color.GREEN,
Color.ORANGE,Color.PINK,Color.RED,Color.YELLOW,Color.WHITE};
private static final Random random = new Random();   //创建随机对象

//随机获取颜色对象
public static Color getColor(){
int i = random.nextInt(color.length);
return color[i];
}

//构造方法
public SleepThreadTest(){
t = new Thread(new Runnable(){
int x = 100;
int y = 100;
public void run(){
while(true){
try{
Thread.sleep(50);
}catch(Exception e){
e.printStackTrace();
}
Graphics graphics = getGraphics();  //不能放在外面
graphics.setColor(getColor());     //设置随机产生的颜色
graphics.drawLine(x, y, x+200, y);   //画直线
y+=5;
if(y>300){
y = 100;
}
}
}
});
t.start();     //启动线程
}

public static void main(String[] args) {
init(new SleepThreadTest(),500,400);

}

//初始化方法
public static void init(JFrame frame,int width,int heigh){
frame.setSize(width,heigh);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

}