What is the purpose of flush() in Java streams?

Question

I was asked this question in an interview, can someone tell me the use of flush() in Java streams?

Answer 1

The flush() method of OutputStream class is used to flush the content of the buffer to the output stream. A buffer is a portion in memory that is used to store a stream of data(characters). That data sometimes will only get sent to an output device, when the buffer is full.

Answer 2

The java.io.Writer.flush() method flushes the stream 

The Java.io.Writer.flush() method flushes the stream. If the stream has saved any characters from the different write() methods in the buffer, write them to their intended destination instantly. 

Declaration: 

public abstract void flush()