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Java example source code file (MultidimensionalCounter.java)

This example Java source code file (MultidimensionalCounter.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

dimensionmismatchexception, integer, iterable, iterator, multidimensionalcounter, nosuchelementexception, notstrictlypositiveexception, outofrangeexception, override, stringbuilder, unsupportedoperationexception, util

The MultidimensionalCounter.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.NoSuchElementException;
import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.NotStrictlyPositiveException;
import org.apache.commons.math3.exception.OutOfRangeException;

/**
 * Converter between unidimensional storage structure and multidimensional
 * conceptual structure.
 * This utility will convert from indices in a multidimensional structure
 * to the corresponding index in a one-dimensional array. For example,
 * assuming that the ranges (in 3 dimensions) of indices are 2, 4 and 3,
 * the following correspondences, between 3-tuples indices and unidimensional
 * indices, will hold:
 * <ul>
 *  <li>(0, 0, 0) corresponds to 0
 *  <li>(0, 0, 1) corresponds to 1
 *  <li>(0, 0, 2) corresponds to 2
 *  <li>(0, 1, 0) corresponds to 3
 *  <li>...
 *  <li>(1, 0, 0) corresponds to 12
 *  <li>...
 *  <li>(1, 3, 2) corresponds to 23
 * </ul>
 *
 * @since 2.2
 */
public class MultidimensionalCounter implements Iterable<Integer> {
    /**
     * Number of dimensions.
     */
    private final int dimension;
    /**
     * Offset for each dimension.
     */
    private final int[] uniCounterOffset;
    /**
     * Counter sizes.
     */
    private final int[] size;
    /**
     * Total number of (one-dimensional) slots.
     */
    private final int totalSize;
    /**
     * Index of last dimension.
     */
    private final int last;

    /**
     * Perform iteration over the multidimensional counter.
     */
    public class Iterator implements java.util.Iterator<Integer> {
        /**
         * Multidimensional counter.
         */
        private final int[] counter = new int[dimension];
        /**
         * Unidimensional counter.
         */
        private int count = -1;
        /**
         * Maximum value for {@link #count}.
         */
        private final int maxCount = totalSize - 1;

        /**
         * Create an iterator
         * @see #iterator()
         */
        Iterator() {
            counter[last] = -1;
        }

        /**
         * {@inheritDoc}
         */
        public boolean hasNext() {
            return count < maxCount;
        }

        /**
         * @return the unidimensional count after the counter has been
         * incremented by {@code 1}.
         * @throws NoSuchElementException if {@link #hasNext()} would have
         * returned {@code false}.
         */
        public Integer next() {
            if (!hasNext()) {
                throw new NoSuchElementException();
            }

            for (int i = last; i >= 0; i--) {
                if (counter[i] == size[i] - 1) {
                    counter[i] = 0;
                } else {
                    ++counter[i];
                    break;
                }
            }

            return ++count;
        }

        /**
         * Get the current unidimensional counter slot.
         *
         * @return the index within the unidimensionl counter.
         */
        public int getCount() {
            return count;
        }
        /**
         * Get the current multidimensional counter slots.
         *
         * @return the indices within the multidimensional counter.
         */
        public int[] getCounts() {
            return MathArrays.copyOf(counter);
        }

        /**
         * Get the current count in the selected dimension.
         *
         * @param dim Dimension index.
         * @return the count at the corresponding index for the current state
         * of the iterator.
         * @throws IndexOutOfBoundsException if {@code index} is not in the
         * correct interval (as defined by the length of the argument in the
         * {@link MultidimensionalCounter#MultidimensionalCounter(int[])
         * constructor of the enclosing class}).
         */
        public int getCount(int dim) {
            return counter[dim];
        }

        /**
         * @throws UnsupportedOperationException
         */
        public void remove() {
            throw new UnsupportedOperationException();
        }
    }

    /**
     * Create a counter.
     *
     * @param size Counter sizes (number of slots in each dimension).
     * @throws NotStrictlyPositiveException if one of the sizes is
     * negative or zero.
     */
    public MultidimensionalCounter(int ... size) throws NotStrictlyPositiveException {
        dimension = size.length;
        this.size = MathArrays.copyOf(size);

        uniCounterOffset = new int[dimension];

        last = dimension - 1;
        int tS = size[last];
        for (int i = 0; i < last; i++) {
            int count = 1;
            for (int j = i + 1; j < dimension; j++) {
                count *= size[j];
            }
            uniCounterOffset[i] = count;
            tS *= size[i];
        }
        uniCounterOffset[last] = 0;

        if (tS <= 0) {
            throw new NotStrictlyPositiveException(tS);
        }

        totalSize = tS;
    }

    /**
     * Create an iterator over this counter.
     *
     * @return the iterator.
     */
    public Iterator iterator() {
        return new Iterator();
    }

    /**
     * Get the number of dimensions of the multidimensional counter.
     *
     * @return the number of dimensions.
     */
    public int getDimension() {
        return dimension;
    }

    /**
     * Convert to multidimensional counter.
     *
     * @param index Index in unidimensional counter.
     * @return the multidimensional counts.
     * @throws OutOfRangeException if {@code index} is not between
     * {@code 0} and the value returned by {@link #getSize()} (excluded).
     */
    public int[] getCounts(int index) throws OutOfRangeException {
        if (index < 0 ||
            index >= totalSize) {
            throw new OutOfRangeException(index, 0, totalSize);
        }

        final int[] indices = new int[dimension];

        int count = 0;
        for (int i = 0; i < last; i++) {
            int idx = 0;
            final int offset = uniCounterOffset[i];
            while (count <= index) {
                count += offset;
                ++idx;
            }
            --idx;
            count -= offset;
            indices[i] = idx;
        }

        indices[last] = index - count;

        return indices;
    }

    /**
     * Convert to unidimensional counter.
     *
     * @param c Indices in multidimensional counter.
     * @return the index within the unidimensionl counter.
     * @throws DimensionMismatchException if the size of {@code c}
     * does not match the size of the array given in the constructor.
     * @throws OutOfRangeException if a value of {@code c} is not in
     * the range of the corresponding dimension, as defined in the
     * {@link MultidimensionalCounter#MultidimensionalCounter(int...) constructor}.
     */
    public int getCount(int ... c)
        throws OutOfRangeException, DimensionMismatchException {
        if (c.length != dimension) {
            throw new DimensionMismatchException(c.length, dimension);
        }
        int count = 0;
        for (int i = 0; i < dimension; i++) {
            final int index = c[i];
            if (index < 0 ||
                index >= size[i]) {
                throw new OutOfRangeException(index, 0, size[i] - 1);
            }
            count += uniCounterOffset[i] * c[i];
        }
        return count + c[last];
    }

    /**
     * Get the total number of elements.
     *
     * @return the total size of the unidimensional counter.
     */
    public int getSize() {
        return totalSize;
    }
    /**
     * Get the number of multidimensional counter slots in each dimension.
     *
     * @return the sizes of the multidimensional counter in each dimension.
     */
    public int[] getSizes() {
        return MathArrays.copyOf(size);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder();
        for (int i = 0; i < dimension; i++) {
            sb.append("[").append(getCount(i)).append("]");
        }
        return sb.toString();
    }
}

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