Sockets are concerned, other streams,
like reading from filesystem are
effective enough for to
be handled normally (with the blocking
read method).

InputStream#available()
is implemented for making a lookup
in the buffer

To take advantage of this, you have
to make a Thread.sleep() for
giving time to the other threads.
In the main-thread those are the other
applications in the OS.

  InputStream in; //from Socket or other blocking stream
  byte buf=new byte[BUFSIZE];
  int r=0;
  do {
     if(in.available()>0) {
       r = in.read(buf);
       doSomethingWith(buf,r);
     }
     Thread.sleep(100/*ms*/);
  } while(!timeOut());

Note, that available can return always
0 in some stream implementations. Then non-blocking-io is impossible.
Timeouts (here manually) can be
defined in the Socket constructor.