Check for incoming data in Java Socket

Question

I'm writing a simple chat in Java, and I want to check if there is some data waiting on BufferedReader . I've read about NIO, but I didn't completely understand it. Here is some of my code:

public void Send(String data)
{
    out.println(data);
}

public String Recv()
{
    if (dataIncomming)
    {
        try {
            return in.readLine();
        } catch (IOException e) {
            System.err.println("Send: Error on BufferedReader.readLine() - IOException");
        }
    }
    else return "";
}

I don't know what to fill into dataIncomming ...

Answer 1

Use the Stream.Available() method. You might also want to wait until the right amount of bytes is received and wait so the Thread is not running 100% of the time.

while(Stream.Available() != 0); //block until there is data

try{  
    return in.readLine();  
} catch (IOException e) {  
    System.err.println("Send: Error on BufferedReader.readLine() - IOException");  
} 

Answer 2

You can use the InputStream.available() method to check how many bytes have currently arrived on the socket's input stream.

public String Recv()
{
    if (in.available() > 0)
    {
        try {
            return in.readLine();
        } catch (IOException e) {
            System.err.println("Send: Error on BufferedReader.readLine() - IOException");
        }
    }
    else return "";
}