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package com.teamscale.commons.utils;

import java.lang.ref.WeakReference;
import java.util.Collections;
import java.util.Map;
import java.util.WeakHashMap;

/**
 * Custom string pool which performs consistently faster when interning a lot of
 * strings.
 * 
 * @link http://java-performance.info/string-intern-in-java-6-7-8/
 */
public class StringPool {

	private static final Map> STRING_POOL = Collections
			.synchronizedMap(new WeakHashMap<>(100000));

	/**
	 * Checks whether we already have a string in the StringPool that it equal to
	 * the given String. If such a String already exists it returns this String
	 * otherwise
	 */
	public static String intern(String str) {
		WeakReference cached = STRING_POOL.get(str);
		if (cached != null) {
			String value = cached.get();
			if (value != null) {
				return value;
			}
		}
		STRING_POOL.put(str, new WeakReference<>(str));
		return str;
	}
}