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 package com.fasterxml.jackson.core.util;
 import java.util.Map;
Singleton class that adds a simple first-level cache in front of regular String.intern() functionality. This is done as a minor performance optimization, to avoid calling native intern() method in cases where same String is being interned multiple times.

Note: that this class extends java.util.LinkedHashMap is an implementation detail -- no code should ever directly call Map methods.

public final class InternCache
    extends LinkedHashMap<String,String>
Size to use is somewhat arbitrary, so let's choose something that's neither too small (low hit ratio) nor too large (waste of memory).

11-Jul-2012, tatu: Also, consider the nasty case of String hashCode() collisions; size needs to be small enough to survive linear list lookup... so let's go down a notch (from 192 to 100)

    private final static int MAX_ENTRIES = 100;
    public final static InternCache instance = new InternCache();
    private InternCache() {
        super(, 0.8f, true);
    protected boolean removeEldestEntry(Map.Entry<String,Stringeldest)
        return size() > ;
    public synchronized String intern(String input)
        String result = get(input);
        if (result == null) {
            result = input.intern();
        return result;
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