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Java example source code file (Incrementor.java)

This example Java source code file (Incrementor.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.

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deprecated, incrementor, maxcountexceededcallback, maxcountexceededexception, nullargumentexception, override

The Incrementor.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 org.apache.commons.math3.exception.MaxCountExceededException;
import org.apache.commons.math3.exception.NullArgumentException;

/**
 * Utility that increments a counter until a maximum is reached, at
 * which point, the instance will by default throw a
 * {@link MaxCountExceededException}.
 * However, the user is able to override this behaviour by defining a
 * custom {@link MaxCountExceededCallback callback}, in order to e.g.
 * select which exception must be thrown.
 *
 * @since 3.0
 * @deprecated Use {@link IntegerSequence.Incrementor} instead.
 */
@Deprecated
public class Incrementor {
    /**
     * Upper limit for the counter.
     */
    private int maximalCount;
    /**
     * Current count.
     */
    private int count = 0;
    /**
     * Function called at counter exhaustion.
     */
    private final MaxCountExceededCallback maxCountCallback;

    /**
     * Default constructor.
     * For the new instance to be useful, the maximal count must be set
     * by calling {@link #setMaximalCount(int) setMaximalCount}.
     */
    public Incrementor() {
        this(0);
    }

    /**
     * Defines a maximal count.
     *
     * @param max Maximal count.
     */
    public Incrementor(int max) {
        this(max,
             new MaxCountExceededCallback() {
                 /** {@inheritDoc} */
                 public void trigger(int max) throws MaxCountExceededException {
                     throw new MaxCountExceededException(max);
                 }
             });
    }

    /**
     * Defines a maximal count and a callback method to be triggered at
     * counter exhaustion.
     *
     * @param max Maximal count.
     * @param cb Function to be called when the maximal count has been reached.
     * @throws NullArgumentException if {@code cb} is {@code null}
     */
    public Incrementor(int max, MaxCountExceededCallback cb)
        throws NullArgumentException {
        if (cb == null){
            throw new NullArgumentException();
        }
        maximalCount = max;
        maxCountCallback = cb;
    }

    /**
     * Sets the upper limit for the counter.
     * This does not automatically reset the current count to zero (see
     * {@link #resetCount()}).
     *
     * @param max Upper limit of the counter.
     */
    public void setMaximalCount(int max) {
        maximalCount = max;
    }

    /**
     * Gets the upper limit of the counter.
     *
     * @return the counter upper limit.
     */
    public int getMaximalCount() {
        return maximalCount;
    }

    /**
     * Gets the current count.
     *
     * @return the current count.
     */
    public int getCount() {
        return count;
    }

    /**
     * Checks whether a single increment is allowed.
     *
     * @return {@code false} if the next call to {@link #incrementCount(int)
     * incrementCount} will trigger a {@code MaxCountExceededException},
     * {@code true} otherwise.
     */
    public boolean canIncrement() {
        return count < maximalCount;
    }

    /**
     * Performs multiple increments.
     * See the other {@link #incrementCount() incrementCount} method).
     *
     * @param value Number of increments.
     * @throws MaxCountExceededException at counter exhaustion.
     */
    public void incrementCount(int value) throws MaxCountExceededException {
        for (int i = 0; i < value; i++) {
            incrementCount();
        }
    }

    /**
     * Adds one to the current iteration count.
     * At counter exhaustion, this method will call the
     * {@link MaxCountExceededCallback#trigger(int) trigger} method of the
     * callback object passed to the
     * {@link #Incrementor(int,MaxCountExceededCallback) constructor}.
     * If not explictly set, a default callback is used that will throw
     * a {@code MaxCountExceededException}.
     *
     * @throws MaxCountExceededException at counter exhaustion, unless a
     * custom {@link MaxCountExceededCallback callback} has been set at
     * construction.
     */
    public void incrementCount() throws MaxCountExceededException {
        if (++count > maximalCount) {
            maxCountCallback.trigger(maximalCount);
        }
    }

    /**
     * Resets the counter to 0.
     */
    public void resetCount() {
        count = 0;
    }

    /**
     * Defines a method to be called at counter exhaustion.
     * The {@link #trigger(int) trigger} method should usually throw an exception.
     */
    public interface MaxCountExceededCallback {
        /**
         * Function called when the maximal count has been reached.
         *
         * @param maximalCount Maximal count.
         * @throws MaxCountExceededException at counter exhaustion
         */
        void trigger(int maximalCount) throws MaxCountExceededException;
    }

    /** Create an instance that delegates everything to a {@link IntegerSequence.Incrementor}.
     * <p>
     * This factory method is intended only as a temporary hack for internal use in
     * Apache Commons Math 3.X series, when {@code Incrementor} is required in
     * interface (as a return value or in protected fields). It should <em>not
     * be used in other cases. The {@link IntegerSequence.Incrementor} class should
     * be used instead of {@code Incrementor}.
     * </p>
     * <p>
     * All methods are mirrored to the underlying {@link IntegerSequence.Incrementor},
     * as long as neither {@link #setMaximalCount(int)} nor {@link #resetCount()} are called.
     * If one of these two methods is called, the created instance becomes independent
     * of the {@link IntegerSequence.Incrementor} used at creation. The rationale is that
     * {@link IntegerSequence.Incrementor} cannot change their maximal count and cannot be reset.
     * </p>
     * @param incrementor wrapped {@link IntegerSequence.Incrementor}
     * @return an incrementor wrapping an {@link IntegerSequence.Incrementor}
     * @since 3.6
     */
    public static Incrementor wrap(final IntegerSequence.Incrementor incrementor) {
        return new Incrementor() {

            /** Underlying incrementor. */
            private IntegerSequence.Incrementor delegate;

            {
                // set up matching values at initialization
                delegate = incrementor;
                super.setMaximalCount(delegate.getMaximalCount());
                super.incrementCount(delegate.getCount());
            }

            /** {@inheritDoc} */
            @Override
            public void setMaximalCount(int max) {
                super.setMaximalCount(max);
                delegate = delegate.withMaximalCount(max);
            }

            /** {@inheritDoc} */
            @Override
            public void resetCount() {
                super.resetCount();
                delegate = delegate.withStart(0);
            }

            /** {@inheritDoc} */
            @Override
            public void incrementCount() {
                super.incrementCount();
                delegate.increment();
            }

        };
    }

}

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