How do you "empty" a StringWriter in Java?

Question

What is the correct way to "empty" a StringWriter in Java so that I can reuse the StringWriter without having to create a new one? Neither StringWriter.flush() nor StringWriter.close() seem to have the desired effect.

In what way do they not have the desired effect? Also, why do you want to reuse it instead of creating a new one? — zigdon, Sep 17 '10 at 18:53
They don't empty the `StringWriter` buffer, which is the effect that I desire. — Derek Mahar, Sep 17 '10 at 19:19
Did you look the code source of StreamWriter flush ^^ ? /** * Flush the stream. */ public void flush() { } — Thomas Decaux, Nov 02 '18 at 16:36

score 65 · Accepted Answer · answered Sep 17 '10 at 18:53

65

How about calling getBuffer().setLength(0)?

answered Sep 17 '10 at 18:53

Jon Skeet

2

If you initially set the StringWriter to a specified size, will this setLength reduce that size to 0? – E.S. Jun 26 '13 at 00:29
2

This keeps the capacity of the buffer the same. If you want to deallocate the memory, use `writer.getBuffer().trimToSize();` after setting the length. – thomas88wp Jul 26 '17 at 14:38

score 2 · Answer 2 · edited Jan 16 '17 at 08:50

2

Alternatively, we could also delete the buffer using the following code:

StringBuffer buf = ****.getBuffer();
buf.delete(0,buf.length());

edited Jan 16 '17 at 08:50

Bugs

answered Jan 16 '17 at 07:55

Exception_al

Does this clear the buffer contents or deallocate the buffer storage? In this case, I want to clear the contents. – Derek Mahar Jan 16 '17 at 16:38
If it deallocates the memory for the cleared Buffer, I am not sure... You could check with buf.capacity() – Exception_al Jan 16 '17 at 16:43
https://docs.oracle.com/javase/8/docs/api/java/lang/StringBuffer.html#delete-int-int- is not clear, but seems to suggest that it does not change the buffer size. – Derek Mahar Jan 16 '17 at 16:49

2 Answers2