Since Java's default string interning has got a lot of bad press, I am looking for an alternative.

Can you suggest an API which is a good alternative to Java string interning? My application uses Java 6. My requirement is mainly to avoid duplicate strings via interning.

Regarding the bad press:

  • String intern is implemented via a native method. And the C implementation uses a fixed size of some 1k entries and scales very poorly for large number of strings.
  • Java 6 stores interned strings in Perm gen. And therefore are not GC'd and possibly lead to perm gen errors. I know this is fixed in java 7 but I can't upgrade to java 7.

Why do I need to use intering?

  • My application is a server app with heap size of 10-20G for different deployments.
  • During profiling we have figured that hundrends of thousands of string are duplicates and we can significantly improve the memory usage by avoiding storing duplicate strings.
  • Memory has been a bottleneck for us and therefore we are targetting it rather than doing any premature optimization.
java string memory string-interning
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