Is String.intern() thread safe

Question

I would like to use String.intern() in Java to save memory (use the internal pool for strings with the same content). I call this method from different threads. Is it a problem?

Answer 1

The short answer to your question is yes. It's thread-safe.

However, you might want to reconsider using this facility to reduce memory consumption. The reason is that you are unable to remove any entires from the list of interned strings. A better solution would be to create your own facility for this. All you'd need is to store your strings in a HashMap like so:

public String getInternedString(String s) {
    synchronized(strings) {
        String found = strings.get(s);
        if(found == null) {
            strings.put(s, s);
            found = s;
        }
        return found;
    }
}