Does BufferedReader.ready() method ensure that readLine() method does not return NULL?

Question

I have such code to read a text file using BufferedReader:

BufferedReader reader=null;
    try {
        reader = new BufferedReader(new FileRea         


        

Answer 1

Here's what the Javadocs have to say:

Tells whether this stream is ready to be read. A buffered character stream is ready if the buffer is not empty, or if the underlying character stream is ready.

So a BufferedReader is considered ready simply if the underlying stream is also ready. Since BufferedReader is a wrapper, this underlying stream could be any Reader implementation; hence the semantics of ready() are those declared on the interface:

Returns true if the next read() is guaranteed not to block for input, false otherwise. Note that returning false does not guarantee that the next read will block.

So you only really get timing guarantees, i.e. that read() will not block. The result of calling ready() tells you absolutely nothing about the content you'll get back from a read() call, and so cannot be used to elide a null check.