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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.flink.runtime.util;

/**
 * Atomic reference counter, which enters a "disposed" state after it reaches a configurable
 * reference count (default 0).
 */
public class AtomicDisposableReferenceCounter {

	private final Object lock = new Object();

	private int referenceCount;

	private boolean isDisposed;

	/** Enter the disposed state when the reference count reaches this number. */
	private final int disposeOnReferenceCount;

	public AtomicDisposableReferenceCounter() {
		this.disposeOnReferenceCount = 0;
	}

	public AtomicDisposableReferenceCounter(int disposeOnReferenceCount) {
		this.disposeOnReferenceCount = disposeOnReferenceCount;
	}

	/**
	 * Increments the reference count and returns whether it was successful.
	 * 

* If the method returns false, the counter has already been disposed. Otherwise it * returns true. */ public boolean increment() { synchronized (lock) { if (isDisposed) { return false; } referenceCount++; return true; } } /** * Decrements the reference count and returns whether the reference counter entered the disposed * state. *

* If the method returns true, the decrement operation disposed the counter. * Otherwise it returns false. */ public boolean decrement() { synchronized (lock) { if (isDisposed) { return false; } referenceCount--; if (referenceCount <= disposeOnReferenceCount) { isDisposed = true; } return isDisposed; } } public int get() { synchronized (lock) { return referenceCount; } } /** * Returns whether the reference count has reached the disposed state. */ public boolean isDisposed() { synchronized (lock) { return isDisposed; } } public boolean disposeIfNotUsed() { synchronized (lock) { if (referenceCount <= disposeOnReferenceCount) { isDisposed = true; } return isDisposed; } } }





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