效果图：

  使用的是Java AWTUtilities API 建议使用JDK1.8 开发工具 IDEA所有代码如下

import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import com.sun.awt.AWTUtilities;
import javax.imageio.ImageIO;
import javax.swing.JDialog;
import javax.swing.JPanel;public class Snow extends JDialog{private static final long serialVersionUID = -6073107021198223228L;//  获取屏幕分辨率public final static int Width = (int) java.awt.Toolkit.getDefaultToolkit().getScreenSize().width;public final static int Height = (int) java.awt.Toolkit.getDefaultToolkit().getScreenSize().height;public static void main(String[] args) {new Snow().setVisible(true);}public Snow(){this.setLocation(0,0);//位置this.setSize(Width, Height);//大小,大小为屏幕分辨率this.setUndecorated(true);//隐藏最大化最小化那一栏，一时想不起叫什么了this.setAlwaysOnTop(true);//窗口始终在最顶上this.setDefaultCloseOperation(0);//防止按Alt+F4关闭hua hua=new hua();this.add(hua);AWTUtilities.setWindowOpaque(this, false);//实现透明窗口建议使用jre1.7版本}
}class hua extends JPanel implements Runnable{//画布private static final long serialVersionUID = -2986761287590314088L;public static ArrayList<xue>list=new ArrayList<xue>();private BufferedImage img;public hua(){try {img=ImageIO.read(new File("snow.png"));//加载雪花图片} catch (IOException e) {e.printStackTrace();}this.setOpaque(false);//设为透明的new Thread(this).start();//启动线程}@Overridepublic void paint(Graphics g) {// TODO 自动生成的方法存根super.paint(g);for(int i=0;i<list.size();i++){xue x=list.get(i);g.drawImage(img, (int)x.x, (int)x.y, x.w, x.h, null);}}@Overridepublic void run() {// TODO 自动生成的方法存根int fps=150;//每秒帧数int time=1000/fps;int ii=0;while(true){long a=System.currentTimeMillis();if(ii>3){new xue();ii=0;}ii++;for(int i=0;i<list.size();i++){//调用所有雪花的run方法list.get(i).run();}repaint();//画雪long b=System.currentTimeMillis();long c=b-a;if(time-c>0)try {Thread.sleep(time-c);} catch (InterruptedException e) {e.printStackTrace();}}}}class xue{//雪0public int w,h;public float x,y,sdx,sdy;public xue(){w=h=(int)(Math.random()*20+10);//随机大小sdx=(float) (Math.random()*0.7+0.3);//x轴移动速度sdy=(float) (Math.random()*0.4+0.3);//y轴移动速度//雪花出现的位置只能在屏幕的上右方double gailv=(double)(Snow.Width+ Snow.Height)/ Snow.Width-1;if(Math.random()<gailv){//雪花在屏幕上方y=-h;x=(int)(Math.random()* Snow.Width);}else{//雪花在屏幕右方x= Snow.Width;y=(int)(Math.random()* Snow.Height);}hua.list.add(this);//添加进集合}public void run(){//雪花的移动//如果雪花超出屏幕范围的话就从集合中删掉if(x+w<0||y> Snow.Height||x+w<0||y> Snow.Height){hua.list.remove(this);}y+=sdy;x-=sdx;}
}

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