/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.el.util;

import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.ConcurrentHashMap;

public final class ConcurrentCache<K,V> {

	private final int size;
	
	private final Map<K,V> eden;
	
	private final Map<K,V> longterm;
	
	public ConcurrentCache(int size) {
		this.size = size;
		this.eden = new ConcurrentHashMap<K,V>(size);
		this.longterm = new WeakHashMap<K,V>(size);
	}
	
	public V get(K k) {
		V v = this.eden.get(k);
		if (v == null) {
			v = this.longterm.get(k);
			if (v != null) {
				this.eden.put(k, v);
			}
		}
		return v;
	}
	
	public void put(K k, V v) {
		if (this.eden.size() >= size) {
			this.longterm.putAll(this.eden);
			this.eden.clear();
		}
		this.eden.put(k, v);
	}
}