/*
 * Copyright (c) 2014, The TridentSDK Team
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     1. Redistributions of source code must retain the above copyright
 *        notice, this list of conditions and the following disclaimer.
 *     2. Redistributions in binary form must reproduce the above copyright
 *        notice, this list of conditions and the following disclaimer in the
 *        documentation and/or other materials provided with the distribution.
 *     3. Neither the name of the The TridentSDK Team nor the
 *        names of its contributors may be used to endorse or promote products
 *        derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL The TridentSDK Team BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package net.tridentsdk.server.threads;

import java.util.ArrayList;
import java.util.Collection;
import java.util.concurrent.*;

public class ConcurrentCache<K, V> {
    private final ConcurrentMap<K, Future<V>> cache = new ConcurrentHashMap<>();

    public V retrieve(K k, Callable<V> callable, ExecutorService executor) {
        while (true) {
            Future<V> future = this.cache.get(k);

            if (future == null) {
                Future<V> task = new FutureTask<>(callable);
                future = this.cache.putIfAbsent(k, task);

                if (future == null) future = executor.submit(callable);
            }

            try {
                return future.get();
            } catch (InterruptedException | ExecutionException e) {
                e.printStackTrace();
            } catch (CancellationException e) {
                this.cache.remove(k, future);
            }
        }
    }

    public V retrieve(K k) {
        Future<V> future = this.cache.get(k);

        if (future == null) return null;

        try {
            return future.get();
        } catch (InterruptedException | ExecutionException e) {
            e.printStackTrace();
        } catch (CancellationException e) {
            this.cache.remove(k, future);
        }

        return null;
    }

    public Collection<V> values() {
        Collection<V> list = new ArrayList<>();

        for (Future<V> v : this.cache.values()) {
            try {
                list.add(v.get());
            } catch (InterruptedException | ExecutionException ignored) {
            }
        }

        return list;
    }
}

@@ -2520,395 +2520,8 @@
  %7D%0A%0A
-    public V retrieve(K k) %7B%0A        Future%3CV%3E future = this.cache.get(k);%0A%0A        if (future == null) return null;%0A%0A        try %7B%0A            return future.get();%0A        %7D catch (InterruptedException %7C ExecutionException e) %7B%0A            e.printStackTrace();%0A        %7D catch (CancellationException e) %7B%0A            this.cache.remove(k, future);%0A        %7D%0A%0A        return null;%0A    %7D%0A%0A
     

Update ConcurrentCache.java