flush : Java Glossary

flush

a method common in I/O classes that effectively does all the normal file or stream close processing, but leaves the file open, or, if you prefer, conceptually closes then instantly reopens the file/stream. flush makes sure everything you have written so far is committed to the hard disk, and the expanded file length is also committed to the disk directory, with the updated lastModified timestamp committed too.

If you crash the system later, you know at least that much is guaranteed to be there on disk waiting for you when you reboot.

When you flush a socket, it pushes every last byte you have written so far out the wire, even if it means sending a tiny packet.

When you flush a console, flush guarantees every byte you have written so far is displayed on screen.

Many constructors have an autofush boolean so that, when true, flushes automatically after every write.

flush is analogous to flushing a toilet. It clears the bowl/buffer of accumulated waste/bytes.

You don’t need to flush just prior to close, because close handles the flushing.

Learning More

Sun’s Javadoc on OutputStream.flush : available:

on the web at java.sun.com
in the current JDK 1.6.0_17 or in the old JDK 1.5.0_22 on your local Windows J: drive.

File
File I/O amanuensis: generates skeleton code using flush
socket

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