java实现一个简单的缓存

import java.util.Map;

import java.util.WeakHashMap;

import java.util.concurrent.ConcurrentHashMap;

import java.util.concurrent.locks.Lock;

import java.util.concurrent.locks.ReentrantLock;

public final class SimpleCache<K,V> {

private final Lock lock = new ReentrantLock();

private final int maxCapacity;

private final Map<K,V> eden;

private final Map<K,V> perm;

public SimpleCache(int maxCapacity) {

this.maxCapacity = maxCapacity;

this.eden = new ConcurrentHashMap<K,V>(maxCapacity);

this.perm= new WeakHashMap<K,V>(maxCapacity);

}

public V get(K k) {

V v = this.eden.get(k);

if (v == null) {

lock.lock();

try{

v = this.perm.get(k);

}finally{

lock.unlock();

}

if (v != null) {

this.eden.put(k, v);

}

}

return v;

}

public void put(K k, V v) {

if (this.eden.size() >= maxCapacity) {

lock.lock();

try{

this.perm.putAll(this.eden);

}finally{

lock.unlock();

}

this.eden.clear();

}

this.eden.put(k, v);

}

}