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Java example source code file (IterationManager.java)

This example Java source code file (IterationManager.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

collection, copyonwritearraylist, deprecated, iterationevent, iterationlistener, iterationmanager, maxcountexceededexception, threading, threads, util

The IterationManager.java Java example source code

/*
 * 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.commons.math3.util;

import java.util.Collection;
import java.util.concurrent.CopyOnWriteArrayList;

import org.apache.commons.math3.exception.MaxCountExceededException;

/**
 * This abstract class provides a general framework for managing iterative
 * algorithms. The maximum number of iterations can be set, and methods are
 * provided to monitor the current iteration count. A lightweight event
 * framework is also provided.
 *
 */
public class IterationManager {

    /** Keeps a count of the number of iterations. */
    private IntegerSequence.Incrementor iterations;

    /** The collection of all listeners attached to this iterative algorithm. */
    private final Collection<IterationListener> listeners;

    /**
     * Creates a new instance of this class.
     *
     * @param maxIterations the maximum number of iterations
     */
    public IterationManager(final int maxIterations) {
        this.iterations = IntegerSequence.Incrementor.create().withMaximalCount(maxIterations);
        this.listeners = new CopyOnWriteArrayList<IterationListener>();
    }

    /**
     * Creates a new instance of this class.
     *
     * @param maxIterations the maximum number of iterations
     * @param callBack the function to be called when the maximum number of
     * iterations has been reached
     * @throws org.apache.commons.math3.exception.NullArgumentException if {@code callBack} is {@code null}
     * @since 3.1
     * @deprecated as of 3.6, replaced with {@link #IterationManager(int,
     * org.apache.commons.math3.util.IntegerSequence.Incrementor.MaxCountExceededCallback)}
     */
    @Deprecated
    public IterationManager(final int maxIterations,
                            final Incrementor.MaxCountExceededCallback callBack) {
        this(maxIterations, new IntegerSequence.Incrementor.MaxCountExceededCallback() {
            /** {@inheritDoc} */
            public void trigger(final int maximalCount) throws MaxCountExceededException {
                callBack.trigger(maximalCount);
            }
        });
    }

    /**
     * Creates a new instance of this class.
     *
     * @param maxIterations the maximum number of iterations
     * @param callBack the function to be called when the maximum number of
     * iterations has been reached
     * @throws org.apache.commons.math3.exception.NullArgumentException if {@code callBack} is {@code null}
     * @since 3.6
     */
    public IterationManager(final int maxIterations,
                            final IntegerSequence.Incrementor.MaxCountExceededCallback callBack) {
        this.iterations = IntegerSequence.Incrementor.create().withMaximalCount(maxIterations).withCallback(callBack);
        this.listeners = new CopyOnWriteArrayList<IterationListener>();
    }

    /**
     * Attaches a listener to this manager.
     *
     * @param listener A {@code IterationListener} object.
     */
    public void addIterationListener(final IterationListener listener) {
        listeners.add(listener);
    }

    /**
     * Informs all registered listeners that the initial phase (prior to the
     * main iteration loop) has been completed.
     *
     * @param e The {@link IterationEvent} object.
     */
    public void fireInitializationEvent(final IterationEvent e) {
        for (IterationListener l : listeners) {
            l.initializationPerformed(e);
        }
    }

    /**
     * Informs all registered listeners that a new iteration (in the main
     * iteration loop) has been performed.
     *
     * @param e The {@link IterationEvent} object.
     */
    public void fireIterationPerformedEvent(final IterationEvent e) {
        for (IterationListener l : listeners) {
            l.iterationPerformed(e);
        }
    }

    /**
     * Informs all registered listeners that a new iteration (in the main
     * iteration loop) has been started.
     *
     * @param e The {@link IterationEvent} object.
     */
    public void fireIterationStartedEvent(final IterationEvent e) {
        for (IterationListener l : listeners) {
            l.iterationStarted(e);
        }
    }

    /**
     * Informs all registered listeners that the final phase (post-iterations)
     * has been completed.
     *
     * @param e The {@link IterationEvent} object.
     */
    public void fireTerminationEvent(final IterationEvent e) {
        for (IterationListener l : listeners) {
            l.terminationPerformed(e);
        }
    }

    /**
     * Returns the number of iterations of this solver, 0 if no iterations has
     * been performed yet.
     *
     * @return the number of iterations.
     */
    public int getIterations() {
        return iterations.getCount();
    }

    /**
     * Returns the maximum number of iterations.
     *
     * @return the maximum number of iterations.
     */
    public int getMaxIterations() {
        return iterations.getMaximalCount();
    }

    /**
     * Increments the iteration count by one, and throws an exception if the
     * maximum number of iterations is reached. This method should be called at
     * the beginning of a new iteration.
     *
     * @throws MaxCountExceededException if the maximum number of iterations is
     * reached.
     */
    public void incrementIterationCount()
        throws MaxCountExceededException {
        iterations.increment();
    }

    /**
     * Removes the specified iteration listener from the list of listeners
     * currently attached to {@code this} object. Attempting to remove a
     * listener which was <em>not previously registered does not cause any
     * error.
     *
     * @param listener The {@link IterationListener} to be removed.
     */
    public void removeIterationListener(final IterationListener listener) {
        listeners.remove(listener);
    }

    /**
     * Sets the iteration count to 0. This method must be called during the
     * initial phase.
     */
    public void resetIterationCount() {
        iterations = iterations.withStart(0);
    }
}

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