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Module containing support classes depending on Java SE 6, Guava 11 and Joda-Time 2.0

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/*
 * Copyright (C) the original author or authors.
 *
 * 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 net.derquinse.common.util.concurrent;

import java.util.concurrent.Executor;
import java.util.concurrent.Future;

import net.derquinse.common.base.Disposable;

import com.google.common.base.Supplier;

/**
 * Interface for suppliers of reference counted disposable objects. A strong reference may be kept
 * to the destination objects, so the reference itself has to be unreachable for the destination
 * object to be gc'd.
 * @param  the type of the disposable object.
 * @author Andres Rodriguez
 */
public interface RefCounted extends Supplier> {
	/**
	 * Returns a new disposable reference. The return value will be valid until it is disposed.
	 * @throws IllegalStateException if the object has been shut down.
	 */
	Disposable get();

	/**
	 * Returns the current number of active references.
	 */
	int getCount();

	/**
	 * Returns the maximum number of active references.
	 */
	int getMaxCount();

	/**
	 * Shuts the reference down. No more references will be provided and when the last one is disposed
	 * the shutdown hook will be submitted to the provided executor. If the reference has been already
	 * shut down this method is a no-op.
	 * @param executor Executor to use for the shutdown hook.
	 * @return A future which result is the shuwdown hook execution time.
	 */
	Future shutdown(Executor executor);

	/**
	 * Shuts the reference down using the calling thread of the last disposed reference.
	 * @see RefCounted#shutdown(Executor)
	 */
	Future shutdown();

}