javaCache实现，简单 ，但是经典

缓存技术，有利于提高程序的性能，但如何实现缓存呢，今天就来介绍一下：

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);
	}
}

至此，简单的缓存已经先后死好了，很简单吧