java實現一個本地緩存工具類

本地緩存實現大概思路，單例模式創建本地緩存實例 + 定時器定時掃描緩存是否過期

代碼如下

package webapp.cache;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;

/**
 * @Author:vic
 * @Date:Created in 16:55 2019/12/27
 * @Description:本地緩存
 */
public class LocalCache {

    /**緩存默認失效時間(毫秒)*/
    private static final long DEFAULT_TIMEOUT = 3600*1000;

    /**緩存清除動作執行間隔(秒)*/
    private static final long TASK_TIME = 1;

    /**緩存存儲的map*/
    private static final ConcurrentHashMap<String,CacheEntity> cacheMap = new ConcurrentHashMap<>();


    public LocalCache() {
    }

    private static LocalCache cache = null;

    public static LocalCache getInstance() {
　　　　　//單例一下
        if (cache == null) {
            cache = new LocalCache();
            new Thread(new TimeoutTimer()).start();
        }

        return cache;
    }

    //定時器線程-用於檢查緩存過期
    static class TimeoutTimer implements Runnable{

        @Override
        public void run(){
            while (true) {
                try {
                    TimeUnit.SECONDS.sleep(TASK_TIME);
                    for (String key:cacheMap.keySet()) {
                        CacheEntity entity = cacheMap.get(key);
                        long now = System.currentTimeMillis();
                        if ((now - entity.getTimeStamp()) >= entity.getExpire()) {
                            cacheMap.remove(key);
                        }
                    }
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /**存儲單元*/
    static class CacheEntity {

        /**值*/
        private Object value;

        /**過期時間(毫秒)*/
        private long expire;

        /**創建時的時間戳*/
        private long timeStamp;

        public Object getValue() {
            return value;
        }

        public void setValue(Object value) {
            this.value = value;
        }

        public long getExpire() {
            return expire;
        }

        public void setExpire(long expire) {
            this.expire = expire;
        }

        public long getTimeStamp() {
            return timeStamp;
        }

        public void setTimeStamp(long timeStamp) {
            this.timeStamp = timeStamp;
        }
    }

    public static boolean set(String key,Object value,long expire) {

        cacheMap.put(key,setEntity(key,value,expire));

        return true;
    }

    public static boolean set(String key,Object value) {

        cacheMap.put(key,setEntity(key,value,DEFAULT_TIMEOUT));

        return true;
    }

    private static CacheEntity setEntity(String key,Object value,long expire){

        CacheEntity entity = new CacheEntity();
        entity.setValue(value);
        entity.setExpire(expire);
        entity.setTimeStamp(System.currentTimeMillis());

        return entity;
    }

    public static Object get(String key) {
        CacheEntity entity = cacheMap.get(key);

        if (entity == null) {
            return null;
        } else {
            Object value = entity.getValue();
            if (value == null) {
                return null;
            }
            return value;
        }
    }

    public static void remove(String key) {
        cacheMap.remove(key);
    }

}

調用示例

String key = "key";
String value = "value";
        
LocalCache cache = LocalCache.getInstance();
cache.set(key,value,5000);
Object result = cache.get(key);
System.out.println(result.toString());