What does InputStream.available() do in Java?

Question

What does InputStream.available() do in Java? I read the documentation, but I still cannot make it out.

The doc says:

Re

Answer 1

Blocking doesn't relate to threading or synchronisation here. Instead it relates to blocking IO (see this for more info). If you issue a request to read, and the channel has none available, a blocking call will wait (or block) until data is available (or the channel is closed, throws an exception etc.)

So why use available() ? So you can determine how many bytes to read, or determine whether you're going to block.

Note that Java has non-blocking IO capabilities as well. See here for more details