How should I read from a buffered reader?

Question

I have the following example of reading from a buffered reader:

while ((inputLine = input.readLine()) != null) {
   System.out.println(\"I got a message from         


        

Answer 1

The reader's readLine() will return a string value when it has something read, an empty string when there isn't anything yet, and null when the connection is closed.

I would recommend wrapping a try/catch around your block of code with the IO function and handle errors appropriately.

Answer 2

When the socket on the other end is closed, the reader should return a null string. This is the condition that you are looking for. To handle the exception, wrap the reading loop in a try/catch block.

 try {
   while ((inputLine = input.readLine()) != null) {
     System.out.println("I got a message from a client: " + inputLine);
   }
 }
 catch (IOException e) {
   System.err.println("Error: " + e);
 }

You might find this tutorial on reading/writing from/to a socket in Java, helpful.

Answer 3

while ((inputLine = input.readLine()) != null) {

Look at each part of the expression:

input.readLine()

Returns a String which will be null if the end of the stream has been reached (or throws an Exception on error).

inputLine = input.readLine()

Assigns this String to inputLine

((inputLine = input.readLine()) != null)

Checks that the String that was assigned is not null (end of stream).