Problem with StringBuffer

Wolfgang Muees wolfgang at
Wed Mar 29 10:38:18 PST 2000

Am Mit, 29 Mär 2000 schrieb Tatu Saloranta:
> I finally found out the reason for 'memory leak' on my Java program,
> and the culprit in this case was StringBuffer - implementation.
> I have a lexer (made with JFLex), that uses StringBuffer for
> constructing
> the strings for certain tokens. The StringBuffer is reused so that each
> time a new such token is getting creted, StringBuffer.setLength(0) is
> called. However, in Kaffe's implementation at least, the actual length
> of the buffer is not changed. This wouldn't be a big problem in itself,
> as there's just one StringBuffer instance... But, alas, as Strings &
> StringBuffers are optimized so that when new String(StringBuffer) is
> called, the character array is actually shared between the string
> and string buffer, until the StringBuffer needs to change the data
> (or length of the buffer via setLength()). The problem here is that
> as soon as I encounter a long token (~4000 chars in this case),
> _all_ tokens after that will use up the same 4k memory

The right solution for this problem is IMO: don't reuse StringBuffer.
It is designed primary as an input buffer for a single string.

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