高效可伸缩的结果缓存

摘要: 高效可伸缩的结果缓存

/**

* 要执行的算法，返回结果v

*/

public interface Computable<A, V> {

public V comput(final A arg);

}

Java代码



/**

* 用于缓存数据

*/

public class Memoizer<A, V> implements Computable<A, V> {

private final ConcurrentMap<A, Future<V>> cache = new ConcurrentHashMap<A, Future<V>>();

private final Computable<A, V> c;

private Memoizer(Computable<A, V> c) {

this.c = c;

}

@Override

public V comput(final A arg) {

while (true) {

Future<V> f = cache.get(arg);

if (f == null) {

Callable<V> eval = new Callable<V>() {

@Override

public V call() throws Exception {

return c.comput(arg);

}

};

FutureTask<V> ft = new FutureTask<V>(eval);

//若没有这个key则put。总是返回oldValue

f = cache.putIfAbsent(arg, ft);

if (f == null) {

f = ft;

ft.run();

}

}

return null;

}

}

}

你看懂了吗？