import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
public class CacheWithExpireUtil {
// 缓存map
private static MapcacheMap =new ConcurrentHashMap();
// 缓存有效期map
private static MapexpireTimeMap =new ConcurrentHashMap();
/**
* 获取指定的value，如果key不存在或者已过期，则返回null
*
* @param key
* @return
*/
public static Object get(String key) {
if (!cacheMap.containsKey(key)) {
return null;
}
if (expireTimeMap.containsKey(key)) {
if (expireTimeMap.get(key) < System.currentTimeMillis()) {// 缓存失效，已过期
return null;
}
}
return cacheMap.get(key);
}
/**
* @param key
* @param
* @return
*/
public static T getT(String key) {
Object obj =get(key);
return obj ==null ?null : (T) obj;
}
/**
* 设置value（不过期）
*
* @param key
* @param value
*/
public static void set(String key, Object value) {
cacheMap.put(key, value);
}
/**
* 设置value
*
* @param key
* @param value
* @param second 过期时间（秒）
*/
public static void set(final String key, Object value,int second) {
final long expireTime = System.currentTimeMillis() + second *1000;
cacheMap.put(key, value);
expireTimeMap.put(key, expireTime);
if (cacheMap.size() >2) {// 清除过期数据
new Thread(new Runnable() {
@Override
public void run() {
// 此处若使用foreach进行循环遍历，删除过期数据，会抛出java.util.ConcurrentModificationException异常
Iterator> iterator =cacheMap.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry entry = iterator.next();
if (expireTimeMap.containsKey(entry.getKey())) {
long expireTime =expireTimeMap.get(key);
if (System.currentTimeMillis() > expireTime) {
iterator.remove();
expireTimeMap.remove(entry.getKey());
}
}
}
}
}).start();
}
}
/**
* key是否存在
*
* @param key
* @return
*/
public static boolean isExist(String key) {
return cacheMap.containsKey(key);
}
/**
* 清除缓存
*
* @param key
*/
public static void remove(String key) {
cacheMap.remove(key);
}
public static void main(String[] args) {
CacheWithExpireUtil.set("testKey_1","testValue_1");
CacheWithExpireUtil.set("testKey_2","testValue_2",10);
CacheWithExpireUtil.set("testKey_3","testValue_3");
CacheWithExpireUtil.set("testKey_4","testValue_4",1);
Object testKey_2 = CacheWithExpireUtil.get("testKey_2");
System.out.println(testKey_2);
}
}
