一个java流量控制小程序

在开发中，常常会遇到文件上传下载流量控制的问题，这是一个小程序，简单的实现了这个功能，可以参考一下

public class FlowControlInputStream extends FilterInputStream{    

    public static void main(String[] args){ 
        try{ 
            byte[] buffer = new byte[8092];        
            int n;       
            long start = System.currentTimeMillis(); 
            FileInputStream in = new FileInputStream("E:\\pic.rar"); 
            //限制流量为10000也就是10000=10kbps 
            FlowControlInputStream fin = new FlowControlInputStream(in, 40000);        
           // fin.update(1000);          
            System.out.println("当前速率："+fin.check()/1000+"kbps"); 
            System.out.println("当前文件大小:"+fin.available()/1024+"kb"); 
            while( (n = fin.read(buffer)) > 0); 
            fin.close();                
            long end = System.currentTimeMillis(); 
            System.out.println("读取文件完成，共花掉"+(end-start)/600+"秒"); 
        }catch(IOException e){ 
            e.printStackTrace(); 
        } 
    } 
  

	private long timestamp; 
    private int maxbps; 
    private int currentbps; 
    private int bytesread; 
    
    //---------------------------------------------------------- 
    //constructor 
    public FlowControlInputStream(InputStream in, int maxbps){ 
        super(in); 
        this.maxbps = maxbps; 
        this.currentbps = 0;        
        this.bytesread = 0; 
        this.timestamp = System.currentTimeMillis(); 
    } 
    
    //---------------------------------------------------------- 
    //decorated methods 
    
    public int read() throws IOException{ 
        synchronized(in){ 
            int avaliable = check(); 
            if(avaliable == 0){ 
                waitForAvailable(); 
                avaliable = check(); 
            } 
            int value = in.read(); 
            update(1); 
            return value; 
        } 
    } 

    public int read(byte[] b) throws IOException{ 
        return read(b, 0, b.length); 
       
    } 

    public int read(byte[] b, int off, int len) throws IOException{ 
        synchronized(in){ 
            int avaliable = check(); 
            if(avaliable == 0){ 
                waitForAvailable();                        
                avaliable = check(); 
            }        
            int n = in.read(b, off, Math.min(len, avaliable)); 
            update(n); 
            return n;   
        } 
    } 

    private int check(){ 
        long now = System.currentTimeMillis(); 
        if(now - timestamp >= 1000){ 
            timestamp = now; 
            currentbps = bytesread; 
            bytesread = 0; 
            return maxbps; 
        }else{ 
            return maxbps - bytesread; 
        } 
    } 

    private void waitForAvailable(){ 
        long time = System.currentTimeMillis() - timestamp; 
        boolean isInterrupted = false; 
        while(time < 1000){ 
            try{ 
                Thread.sleep(1000 - time); 
            }catch(InterruptedException e){ 
                isInterrupted = true; 
            } 
            time = System.currentTimeMillis() - timestamp; 
        } 
        if(isInterrupted) 
            Thread.currentThread().interrupt(); 
        return; 
        
    } 

    private void update(int n){ 
        bytesread += n; 
    } 
    
    public int getCurrentbps(){ 
        return currentbps; 
    } 
} 

代码很简单！