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package com.dexcoder.commons.cache;

import java.util.HashMap;
import java.util.Iterator;

/**
 * LFU缓存实现
 *
 * Created by liyd on 9/25/14.
 */
public class LFUCache extends AbstractCacheMap {

    /**
     * 构造方法
     *
     * @param cacheSize
     * @param defaultExpire
     */
    public LFUCache(int cacheSize, long defaultExpire) {
        super(cacheSize, defaultExpire);
        cacheMap = new HashMap>(cacheSize + 1);
    }

    /**
     * 实现删除过期对象 和 删除访问次数最少的对象 
     *
     */
    @Override
    protected int eliminateCache() {
        Iterator> iterator = cacheMap.values().iterator();
        int count = 0;
        long minAccessCount = Long.MAX_VALUE;
        while (iterator.hasNext()) {
            CacheObject cacheObject = iterator.next();

            if (cacheObject.isExpired()) {
                iterator.remove();
                count++;
                continue;
            } else {
                //记录下最少的访问次数
                minAccessCount = Math.min(cacheObject.accessCount, minAccessCount);
            }
        }

        if (count > 0) {
            return count;
        }

        if (minAccessCount != Long.MAX_VALUE) {

            iterator = cacheMap.values().iterator();

            while (iterator.hasNext()) {
                CacheObject cacheObject = iterator.next();

                cacheObject.accessCount -= minAccessCount;

                if (cacheObject.accessCount <= 0) {
                    iterator.remove();
                    count++;
                }

            }

        }

        return count;
    }
}