- /**
- * 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？
