https://github.com/Terracotta-OSS/offheap-store/: A library that offers data structures allocated off the java heap. 
/* 
 * Copyright 2015 Terracotta, Inc., a Software AG company.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.terracotta.offheapstore.pinning;

import java.util.concurrent.ConcurrentMap;

public interface PinnableCache<K, V> extends ConcurrentMap<K, V> {

  boolean isPinned(Object key);

  void setPinning(K key, boolean pinned);

  V putPinned(final K key, final V value);

  V getAndPin(final K key);
}