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A library for orchestrating beans and asynchronous events using regular POJOs rather than XML

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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.servicemix.beanflow;

/**
 * Represents a piece of state which can be accessed in a multi threaded way
 * rather like {@link java.util.concurrent.atomic.AtomicReference} but which
 * also supports the use of listeners to be notified when the state changes.
 * 
 * @version $Revision: $
 */
public interface State {

    /**
     * Returns the current value of the state
     */
    public T get();

    /**
     * Sets the current value
     */
    public void set(T value);

    /**
     * Sets the state to a new value and return the old value
     */
    public T getAndSet(T value);

    /**
     * If the current state is the expected value then set it to the given new
     * value and return true otherwise return false
     */
    public boolean compareAndSet(T expected, T newValue);

    /**
     * Add a task to be executed if the state changes
     */
    public void addRunnable(Runnable listener);

    /**
     * Remove a task
     */
    public void removeRunnable(Runnable listener);

    /**
     * Returns true if the current value is equal to the given value
     */
    public boolean is(T that);

    /**
     * Return true if the current value is equal to any of the given values
     */
    public boolean isAny(T... values);

}