org.apache.mahout.fpm.pfpgrowth.fpgrowth.LeastKCache.java Source code

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Here is the source code for org.apache.mahout.fpm.pfpgrowth.fpgrowth.LeastKCache.java

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/**
 * 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.mahout.fpm.pfpgrowth.fpgrowth;

import com.google.common.collect.Maps;

import java.util.Collections;
import java.util.Map;
import java.util.PriorityQueue;

public class LeastKCache<K extends Comparable<? super K>, V> {

    private final int capacity;
    private final Map<K, V> cache;
    private final PriorityQueue<K> queue;

    public LeastKCache(int capacity) {
        this.capacity = capacity;
        cache = Maps.newHashMapWithExpectedSize(capacity);
        queue = new PriorityQueue<K>(capacity + 1, Collections.reverseOrder());
    }

    public final V get(K key) {
        return cache.get(key);
    }

    public final void set(K key, V value) {
        if (!contains(key)) {
            queue.add(key);
        }
        cache.put(key, value);
        while (queue.size() > capacity) {
            K k = queue.poll();
            cache.remove(k);
        }
    }

    public final long size() {
        return cache.size();
    }

    public final boolean contains(K key) {
        return cache.containsKey(key);
    }

}