snow.java

java经典的源代码 我非常喜欢这个源代码 对于编程很有好处

import java.util.Random;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class snow extends Applet implements Runnable{

  Thread mainThread;
  Image im,gAlc[];
  Random rand;
  int stop,snows,wind,threadSleep;
  int[] snowX,snowY;
  long stopTime=0;
  Dimension dim;
  MediaTracker mt;
  public snow() {
  }
  String getParameter(String s1,String s2){
    String s=getParameter(s1);
    return (s!=null)?s:s2;
  }
  int getParameter(String s1,int s2, int max, int min){
    String s=getParameter(s1);
    if(s!=null){
      if((s2=Integer.parseInt(s))> max)
        return max;
      else if(s2<min)
        return min;
      else return s2;
    }
    else return s2;
  }
  //Initialize the applet
  public void init() {
    rand=new Random();
    dim=getSize();
    im=createImage(dim.width,dim.height);
    snows=getParameter("Snows",100,500,0);
    snowX=new int[snows];
    snowY=new int[snows];
    for(int i=0;i<snows;i++){
      snowX[i]=rand.nextInt()%(dim.width/2)+dim.width/2;
      snowY[i]=rand.nextInt()%(dim.height/2)+dim.height/2;
    }
    mt=new MediaTracker(this);
    gAlc=new Image[1];
    gAlc[0]=getImage(getDocumentBase(),getParameter("graphic","leaf.gif"));
    mt.addImage(gAlc[0],0);
    try{
      mt.waitForID(0);
    }
    catch(InterruptedException ex){
      return;
    }
    stop=0;
  }
  public void start(){
    if(mainThread==null){
      mainThread=new Thread(this);
      mainThread.start();
    }
  }
  public void stop(){
    mainThread=null;
  }
  public void run(){
    while(mainThread!=null){
      try{
        Thread.sleep(threadSleep);
      }
      catch(InterruptedException ex){
        return ;
      }
      repaint();
    }
  }
  public void drawBackSnow(Graphics g){
    g.setColor(Color.white);
    for(int i=0;i<snows;i++){
      g.fillOval(snowX[i],snowY[i],3,3);
      snowX[i]+=rand.nextInt()%2+wind;
      snowY[i]+=(rand.nextInt()%6+5)/5+1;
      if(snowX[i]>=dim.width)
        snowX[i]=0;
      if(snowX[i]<0)
        snowX[i]=dim.width-1;
      if(snowY[i]>=dim.height||snowY[i]<0){
        snowX[i]=Math.abs(rand.nextInt()%dim.width);
        snowY[i]=0;
        }
    }
    wind=rand.nextInt()%5-2;
  }
  public void paint(Graphics g){
    im.getGraphics().setColor(Color.black);
    im.getGraphics().fillRect(0,0,dim.width,dim.height);
    im.getGraphics().drawImage(gAlc[0],0,0,this);
    drawBackSnow(im.getGraphics());
    g.drawImage(im,0,0,null);
  }
  public void updata(Graphics g){
    paint(g);
  }
}