i/o java advanced

Question

I noticed that the read (abstract) method of inputStream has different implementations.
in somewhere like System.in and Sockets if reaches to end it waits for new input and blocks Thread. but in file it returns -1 if reaches to end of file.
explain to me.
also explain that is" inputStream available method" reliable to detect that stream reaches to end? despite new input.

Answer 1

Some types of InputStream eg from keyboard do not have the end, but you can stop reading it.
File has exact number of bytes, it is easy to say where is end of file.

by keyboard input available() returns how many unreaded bytes are in buffer,
not bytes to end of stream

also it is possible to simulate end by pressing ctrl+d or ctrl+z then read() returns -1