package com.fasterxml.jackson.core.util;
import java.util.Map;
import java.util.LinkedHashMap;
/**
* 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.
*<p>
* Note: that this class extends {@link LinkedHashMap} is an implementation
* detail -- no code should ever directly call Map methods.
*/
@SuppressWarnings("serial")
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).
*<p>
* 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(MAX_ENTRIES, 0.8f, true);
}
@Override
protected boolean removeEldestEntry(Map.Entry<String,String> eldest)
{
return size() > MAX_ENTRIES;
}
public synchronized String intern(String input)
{
String result = get(input);
if (result == null) {
result = input.intern();
put(result, result);
}
return result;
}
}