原github地址： Java-ConcurrentHashMap實現快取，（快取數量，過期時間，過期快取清理）

大佬是下面這位，先儲存一份程式碼，(●’◡’●)

原封不動copy一份儲存

package cn.yan.study.utils.cache;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.*;
import java.util.concurrent.*;

/**
 * Created
 * User  wankunYan
 * Date  2018/6/26
 * Time  20:32
 */
 

public class ConcurrentHashMapCacheUtils {

    private static Logger LOGGER = LoggerFactory.getLogger(ConcurrentHashMapCacheUtils.class);

    /**
     * 快取最大個數
     */
    private static final Integer CACHE_MAX_NUMBER = 100;
    /**
     * 當前快取個數
     */
    private static Integer CURRENT_SIZE = 0;
    /**
     * 時間一分鐘
     */
 

    static Long ONE_MINUTE = 1 * 60 * 1000L;
    /**
     * 快取物件
     */
    private static final Map<String, CacheObj> CACHE_OBJECT_MAP = new ConcurrentHashMap<>();
    /**
     * 這個記錄了快取使用的最後一次的記錄，最近使用的在最前面
     */
    private static final List<String> CACHE_USE_LOG_LIST = new LinkedList
 
<>();
    /**
     * 清理過期快取是否在執行
     */
    private static Boolean CLEAN_THREAD_IS_RUN = false;

//    /**
//     * 清理執行緒的
//     */
//    private static ExecutorService executor = Executors.newSingleThreadExecutor();


    /**
     * 設定快取
     */
    public static void setCache(String cacheKey, Object cacheValue, long cacheTime) {
        Long ttlTime = null;
        if (cacheTime <= 0L) {
            if (cacheTime == -1L) {
                ttlTime = -1L;
            } else {
                return;
            }
        }
        checkSize();
        saveCacheUseLog(cacheKey);
        CURRENT_SIZE = CURRENT_SIZE + 1;
        if (ttlTime == null) {
            ttlTime = System.currentTimeMillis() + cacheTime;
        }
        CacheObj cacheObj = new CacheObj(cacheValue, ttlTime);
        CACHE_OBJECT_MAP.put(cacheKey, cacheObj);
        LOGGER.info("have set key :" + cacheKey);
    }

    /**
     * 設定快取
     */
    public static void setCache(String cacheKey, Object cacheValue) {
        setCache(cacheKey, cacheValue, -1L);
    }

    /**
     * 獲取快取
     */
    public static Object getCache(String cacheKey) {
        startCleanThread();
        if (checkCache(cacheKey)) {
            saveCacheUseLog(cacheKey);
            return CACHE_OBJECT_MAP.get(cacheKey).getCacheValue();
        }
        return null;
    }

    public static boolean isExist(String cacheKey) {
        return checkCache(cacheKey);
    }

    /**
     * 刪除所有快取
     */
    public static void clear() {
        LOGGER.info("have clean all key !");
        CACHE_OBJECT_MAP.clear();
        CURRENT_SIZE = 0;
    }

    /**
     * 刪除某個快取
     */
    public static void deleteCache(String cacheKey) {
        Object cacheValue = CACHE_OBJECT_MAP.remove(cacheKey);
        if (cacheValue != null) {
            LOGGER.info("have delete key :" + cacheKey);
            CURRENT_SIZE = CURRENT_SIZE - 1;
        }
    }

    /**
     * 判斷快取在不在,過沒過期
     */
    private static boolean checkCache(String cacheKey) {
        CacheObj cacheObj = CACHE_OBJECT_MAP.get(cacheKey);
        if (cacheObj == null) {
            return false;
        }
        if (cacheObj.getTtlTime() == -1L) {
            return true;
        }
        if (cacheObj.getTtlTime() < System.currentTimeMillis()) {
            deleteCache(cacheKey);
            return false;
        }
        return true;
    }

    /**
     * 刪除最近最久未使用的快取
     */
    private static void deleteLRU() {
        LOGGER.info("delete Least recently used run!");
        String cacheKey = CACHE_USE_LOG_LIST.remove(CACHE_USE_LOG_LIST.size() - 1);
        deleteCache(cacheKey);
    }

    /**
     * 刪除過期的快取
     */
    static void deleteTimeOut() {
        LOGGER.info("delete time out run!");
        List<String> deleteKeyList = new LinkedList<>();
        for(Map.Entry<String, CacheObj> entry : CACHE_OBJECT_MAP.entrySet()) {
            if (entry.getValue().getTtlTime() < System.currentTimeMillis() && entry.getValue().getTtlTime() != -1L) {
                deleteKeyList.add(entry.getKey());
            }
        }

        for (String deleteKey : deleteKeyList) {
            deleteCache(deleteKey);
        }
        LOGGER.info("delete cache count is :" + deleteKeyList.size());

    }

    /**
     * 檢查大小
     * 噹噹前大小如果已經達到最大大小
     * 首先刪除過期快取，如果過期快取刪除過後還是達到最大快取數目
     * 刪除最久未使用快取
     */
    private static void checkSize() {
        if (CURRENT_SIZE >= CACHE_MAX_NUMBER) {
            deleteTimeOut();
        }
        if (CURRENT_SIZE >= CACHE_MAX_NUMBER) {
            deleteLRU();
        }
    }

    /**
     * 儲存快取的使用記錄
     */
    private static synchronized void saveCacheUseLog(String cacheKey) {
        CACHE_USE_LOG_LIST.remove(cacheKey);
        CACHE_USE_LOG_LIST.add(0,cacheKey);
    }

    /**
     * 設定清理執行緒的執行狀態為正在執行
     */
    static void setCleanThreadRun() {
        CLEAN_THREAD_IS_RUN = true;
    }

    /**
     * 開啟清理過期快取的執行緒
     */
    private static void startCleanThread() {
        if (!CLEAN_THREAD_IS_RUN) {
            new Thread(new CleanTimeOutThread()).start();
//            executor.submit(new CleanTimeOutThread());
        }
    }

    public static void showUtilsInfo() {
        System.out.println("clean time out cache is run :" + CLEAN_THREAD_IS_RUN);
        System.out.println("cache max count is :" + CACHE_MAX_NUMBER);
        System.out.println("cache current count is :" + CURRENT_SIZE);
        System.out.println("cache object map is :" + CACHE_OBJECT_MAP.toString());
        System.out.println("cache use log list is :" + CACHE_USE_LOG_LIST.toString());

    }

    public static void main(String[] args) {

        for (int i = 0; i < 100; i++) {
            try {
                Thread.sleep(2 * 1000L);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            ConcurrentHashMapCacheUtils.setCache("my_cache_key_" + i, i, 60*1000);
        }

        for (int i = 0; i < 100; i++) {
            if (i > 10) {
                ConcurrentHashMapCacheUtils.getCache("test");
            }
            try {
                Thread.sleep(2 * 1000L);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            ConcurrentHashMapCacheUtils.showUtilsInfo();
        }

    }



}

class CacheObj {
    /**
     * 快取物件
     */
    private Object CacheValue;
    /**
     * 快取過期時間
     */
    private Long ttlTime;

    CacheObj(Object cacheValue, Long ttlTime) {
        CacheValue = cacheValue;
        this.ttlTime = ttlTime;
    }

    Object getCacheValue() {
        return CacheValue;
    }

    Long getTtlTime() {
        return ttlTime;
    }

    @Override
    public String toString() {
        return "CacheObj{" +
                "CacheValue=" + CacheValue +
                ", ttlTime=" + ttlTime +
                '}';
    }
}

/**
 * 每一分鐘清理一次過期快取
 */
class CleanTimeOutThread implements Runnable{

    @Override
    public void run() {
        ConcurrentHashMapCacheUtils.setCleanThreadRun();
        while (true) {
            System.out.println("clean thread run ");
            ConcurrentHashMapCacheUtils.deleteTimeOut();
            try {
                Thread.sleep(ConcurrentHashMapCacheUtils.ONE_MINUTE);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}