What sense does it make to flush a StringWriter in Java?

Question

StringWriter has a flush function. What does it mean to flush a string buffer?

score 26 · Accepted Answer · answered Sep 20 '12 at 08:10

26

It must have an implementation of flush() because in its superclass Writer that's an abstract method, and StringWriter is not an abstract class. However, if you look at the source code of StringWriter.flush(), which you can find in the file src.zip in your JDK installation directory, you'll see:

/**
 * Flush the stream.
 */
public void flush() {
}

In other words, it does nothing. (There are ofcourse other subclasses of Writer where flush() does do something useful).

The person who implemented this method could have documented that it doesn't do anything, but they didn't.

answered Sep 20 '12 at 08:10

Jesper

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@mishadoff For that, see the answers by others on your question. Also the API documentation of `java.io.Writer.flush()` explains what this method is for. – Jesper Sep 20 '12 at 08:14
I mean exact this implementation of `flush` :) – mishadoff Sep 20 '12 at 08:14
9

@mishadoff As you see, it does nothing. What's to not understand about that? – Jesper Sep 20 '12 at 08:15

Stefan · Answer 2 · 2012-09-20T08:19:26.363

2

In general a flush forces a buffer to write its content to the destination, for example writing the bytes to the file on the harddisk.

edited Sep 20 '12 at 08:19

answered Sep 20 '12 at 08:09

Stefan

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StringWriter writes to memory and not to a hard disk. – ceving Sep 20 '12 at 08:10
1

yeah, I just edited to make it more general. thanks for advice. – Stefan Sep 20 '12 at 08:11
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You didn't make it into an answer to OP's question, though. We can safely assume this is what OP knows and is in fact the reason why he asked the question. – Marko Topolnik Sep 20 '12 at 09:17

What sense does it make to flush a StringWriter in Java?

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