//无限星空 wxxk.java
import java.awt.*;
//star类
class Star {
int H, V;
int x, y, z;
int type;

//构造函数
Star( int width, int height, int depth, int type )
{
this.type = type;
H = width/2;
V = height/2;
x = (int)(Math.random()*width) - H;
y = (int)(Math.random()*height) - V;
if( (x == 0) && (y == 0 ) ) x = 10;
z = (int)(Math.random()*depth);
}

//画星星函数
public void Draw( Graphics g, double rot )
{
double X, Y;
int h, v, hh, vv;
int d;
z-=2;
if( z < -63 ) z = 100;
hh = (x*64)/(64+z);
vv = (y*64)/(64+z);
X = (hh*Math.cos(rot))-(vv*Math.sin(rot));
Y = (hh*Math.sin(rot))+(vv*Math.cos(rot));
h = (int)X+H;
v = (int)Y+V;
if( (h < 0) || (h > (2*H))) z = 100;
if( (v < 0) || (v > (2*H))) z = 100;
GrayMe(g);
if( type == 0 )
{
d=(100-z)/50;
if( d == 0 ) d = 1;
g.fillRect( h, v, d, d );
}
else
{
d=(100-z)/20;
g.drawLine( h-d, v, h+d, v );
g.drawLine( h, v-d, h, v+d );
if( z < 50 ) {
d/=2;
g.drawLine( h-d, v-d, h+d, v+d );
g.drawLine( h+d, v-d, h-d, v+d );
}
}
}

//设置颜色函数
public void GrayMe(Graphics g)
{
if ( z > 50 )
{
g.setColor( Color.gray );
}
else if ( z > 25 )
{
g.setColor( Color.lightGray );
}
else
{
g.setColor( Color.white );
}
}
}

// wxxk 类
public class wxxk extends java.applet.Applet implements Runnable
{

//变量定义
int Width, Height;
Thread me = null;
boolean suspend = false;
Image im;
Graphics offscreen;
double rot, dx, ddx;

int speed, stars, type;
double defddx, max;
Star pol[]; 

//初始化函数
public void init()
{
rot = 0;
dx=0;
ddx=0;
Width = size().width;
Height = size().height;

String theSpeed = getParameter( "speed" );
Show( "speed", theSpeed );
speed = (theSpeed == null ) ? 50 : Integer.valueOf( theSpeed ).intValue();

String theStars = getParameter( "stars" );
Show( "stars", theStars );
stars = (theStars == null ) ? 30 : Integer.valueOf( theStars ).intValue();

String theType = getParameter( "type" );
Show( "type", theType );
type = (theType == null ) ? 0 : Integer.valueOf( theType ).intValue();

String theRot = getParameter( "spin" );
Show( "spin", theRot );
rot = (theRot == null) ? 0 : Double.valueOf( theRot ).doubleValue();

String theMax = getParameter( "maxspin" );
Show( "maxspin", theRot );
max = (theMax == null) ? .1 : Double.valueOf( theMax ).doubleValue();

String theddx = getParameter( "ddx" );
Show( "ddx", theddx );
defddx = (theddx == null) ? .005 : Double.valueOf( theddx ).doubleValue();

try
{
im = createImage( Width, Height );
offscreen = im.getGraphics();
}
catch( Exception e)
{
offscreen = null;
}
pol = new Star[stars];
for( int i = 0; i < stars; i++ )
pol[i] = new Star( Width, Height, 100, type );
}

//画屏函数
public void paint( Graphics g )
{
if( offscreen != null )
{
paintMe( offscreen );
g.drawImage( im, 0, 0, this );
}
else
{
paintMe( g );
}
}

//着色
public void paintMe( Graphics g )
{
g.setColor( Color.black );
g.fillRect( 0, 0, Width, Height );

for( int i = 0; i < stars; i++ )
pol[i].Draw( g, rot );
}

//启动线程函数
public void start()
{
if( me == null )
{
me = new Thread( this );
me.start();
}
}

//停止线程
public void stop()
{
if( me != null )
{
me.stop();
me = null;
}
}

//运行
public void run()
{
while( me != null )
{
rot += dx;
dx += ddx;
if( dx > max ) ddx=-defddx;
if( dx < -max) ddx=defddx;
try { Thread.sleep( speed ); }
catch (InterruptedException e){}
repaint();
}
}

//更新屏幕
public void update( Graphics g )
{
paint( g );
}

//响应按下鼠标
public boolean mouseDown( java.awt.Event evt, int x, int y )
{
ddx = (ddx == 0) ? defddx : 0;
return true;
}

public void Toggle( )
{
if( me != null )
{
if( suspend )
{
me.resume();
}
else
{
me.suspend();
}
suspend = !suspend;
}
}

//显示函数
public void Show( String theString, String theValue )
{
if( theValue == null )
{
System.out.println( theString + " : null");
}
else
{
System.out.println( theString + " : " + theValue );
}
}
}