dubbo --- LRUCache简单实现 dubbo

import java.util.LinkedHashMap; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; public class LRUCache extends LinkedHashMap { private static final long serialVersionUID = -5167631809472116969L; private static final float DEFAULT_LOAD_FACTOR = 0.75f; private static final int DEFAULT_MAX_CAPACITY = 1000; private volatile int maxCapacity; private final Lock lock = new ReentrantLock(); public LRUCache() { this(DEFAULT_MAX_CAPACITY); }public LRUCache(int maxCapacity) { super(16, DEFAULT_LOAD_FACTOR, true); this.maxCapacity = maxCapacity; }@Override protected boolean removeEldestEntry(java.util.Map.Entry eldest) { return size() > maxCapacity; }@Override public boolean containsKey(Object key) { try { lock.lock(); return super.containsKey(key); } finally { lock.unlock(); } }@Override public V get(Object key) { try { lock.lock(); return super.get(key); } finally { lock.unlock(); } }@Override public V put(K key, V value) { try { lock.lock(); return super.put(key, value); } finally { lock.unlock(); } }@Override public V remove(Object key) { try { lock.lock(); return super.remove(key); } finally { lock.unlock(); } }@Override public int size() { try { lock.lock(); return super.size(); } finally { lock.unlock(); } }@Override public void clear() { try { lock.lock(); super.clear(); } finally { lock.unlock(); } } public int getMaxCapacity() { return maxCapacity; } public void setMaxCapacity(int maxCapacity) { this.maxCapacity = maxCapacity; }}

利用LinkedHashMap扩展实现简单的LRUCache，主要两点：
1.重写removeEldestEntry方法，决定何时移除最旧条目
2.关键方法加锁，如put、get

说明：
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