Question

As per the java docs, invoking close() on any java.io Streams automatically invokes flush(). But I have seen in lot of examples, even in production codes, developers have explicitly used flush() just before close(). In what conditions we need to use flush() just before close()?

Answer 1

Developer get into a habit of calling flush() after writing something which must be sent.

IMHO Using flush() then close() is common when there has just been a write e.g.

// write a message
out.write(buffer, 0, size);
out.flush();

// finished
out.close();

As you can see the flush() is redundant, but means you are following a pattern.