android开发常用的缓存策略详解（3）- 缓存中的时间超过我们设定的值，将其删除

提供缓存的特殊功能：如果某些缓存对象的时间超过定义值，则该对象将从缓存中删除

public class LimitedAgeMemoryCache<K, V> implements MemoryCacheAware<K, V> {

private final MemoryCacheAware<K, V> cache;

private final long maxAge;
private final Map<K, Long> loadingDates = Collections.synchronizedMap(new HashMap<K, Long>());

/**
* @param cache  Wrapped memory cache
* @param maxAge Max object age <b>(in seconds)</b>. If object age will exceed this value then it'll be removed from
*               cache on next treatment (and therefore be reloaded).
*/
public LimitedAgeMemoryCache(MemoryCacheAware<K, V> cache, long maxAge) {
this.cache = cache;
this.maxAge = maxAge * 1000; // to milliseconds
}

@Override
public boolean put(K key, V value) {
boolean putSuccesfully = cache.put(key, value);
if (putSuccesfully) {
loadingDates.put(key, System.currentTimeMillis());
}
return putSuccesfully;
}

@Override
public V get(K key) {
Long loadingDate = loadingDates.get(key);
if (loadingDate != null && System.currentTimeMillis() - loadingDate > maxAge) {
cache.remove(key);
loadingDates.remove(key);
}//判断如果超过了预设的时间进行响应的删除

return cache.get(key);
}

@Override
public void remove(K key) {
cache.remove(key);
loadingDates.remove(key);
}

@Override
public Collection<K> keys() {
return cache.keys();
}

@Override
public void clear() {
cache.clear();
loadingDates.clear();
}