This answers your question: http://docs.oracle.com/javase/8/docs/api/java/io/OutputStream.html#flush-- http://docs.oracle.com/javase/8/docs/api/java/io/OutputS

This answers your question: http://docs.oracle.com/javase/8/docs/api/java/io/OutputStream.html#flush-- http://docs.oracle.com/javase/8/docs/api/java/io/OutputStrea... It's only logical if you think about the bigger picture. Does Java have access to the underlying disk device or does it work with the filesystem? Which component is responsible for the filesystem?