为什么is.avaliable()返回是0，而有的时候是成功的。

客户端发送一字符串给服务端，服务端输入流调用avaliable()方法返回是0；

同样，服务端返回信息给客户端，客户端输入流调用avaliable()方法返回是0；

服务端

package com.longqihai.server;

import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.ServerSocket; import java.net.Socket;

public class Server {  public static void main(String[] args) {   ServerSocket acceptScoket = null;   try {     acceptScoket = new ServerSocket(9999);     Socket socket = acceptScoket.accept();     InputStream is = socket.getInputStream();     OutputStream os = socket.getOutputStream();         byte[] b = new byte[is.available()];     while(is.available()>0){      is.read(b);     }         System.out.println("客户端:"+new String(b));         os.write(new String("你好我收到了").getBytes());     os.flush();     System.out.println("执行完成了");     is.close();     os.close();     socket.close();   } catch (IOException e) {    e.printStackTrace();   }     } }

客户端：

package com.longqihai.client2;

import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.Socket; import java.net.UnknownHostException;

public class Client {  public static void main(String[] args) throws UnknownHostException, IOException {   Socket socket = new Socket("127.0.0.1",9999);   InputStream is = socket.getInputStream();   OutputStream os = socket.getOutputStream();      os.write(new String("我来看你了").getBytes());   os.flush();      byte[] b = new byte[1024];   if(is.available()>0)   is.read(b);   System.out.println("12:"+new String(b));      is.close();   os.close();   socket.close();  } }