如何检查来自客户端的输入流是否为int数据？

Question

In my client-server program, the client should be able to send string and int value. The server will accept and do corresponding operation only when it is a string . Otherwise, if its an int , the server shouln't be able to handle it (or do nothing with it). How do I implement this logic inside an if statement. I was trying with something like this, but hasNextInt() method shows error:

if(!incomingInput.hasNextInt){
//do nothing
}

This is the part where I am working in:

   if (msgFromClient != null && !msgFromClient.hasNextInt()) {
                    OutputStream clientOut = client.getOutputStream();
                    PrintWriter pw = new PrintWriter(clientOut, true);
                    String ansMsg = "Hello, " + msgFromClient;
                    pw.println(ansMsg);

                }

Answer 1

Based on the code you've posted, it looks like you're just taking the value from the stream and parsing it as a string. If you take it as a string, you could call

Integer.parseInt(ansMsg);

Which will throw a NumberFormatException if the value is not an integer. At this point you can handle the exception as you like (by doing nothing). You'd need to use a try catch statement, but that's one way to go about it.

Answer 2

   try{
      int num = Integer.parseInt(str);
      //if int
    } catch (NumberFormatException e) {

      return; //Do nothing.
 }