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This artifact provides efficient implementations for various collection data structures (esp. linked lists and priority queues), which have very insufficient implementation in the Java Collections Framework that makes it hard or even impossible to exploit their efficiencies.

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/* Copyright (C) 2013-2019 TU Dortmund
 * This file is part of AutomataLib, http://www.automatalib.net/.
 *
 * Licensed 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 net.automatalib.commons.smartcollections;

/**
 * Utility methods for arrays.
 *
 * @author frohme
 */
public final class ArrayUtil {

    private ArrayUtil() {
        throw new AssertionError("Should not be instantiated");
    }

    /**
     * A convenient method for calling {@code computeNewCapacity(length, requiredCapacity, 0)}.
     *
     * @param length
     *         the current length of the array
     * @param requiredCapacity
     *         the immediately required capacity
     *
     * @return the size of an array that is guaranteed to hold {@code requiredCapacity} number of elements.
     *
     * @see #computeNewCapacity(int, int, int)
     */
    public static int computeNewCapacity(int length, int requiredCapacity) {
        return computeNewCapacity(length, requiredCapacity, 0);
    }

    /**
     * Computes the size of an array that is required to hold {@code requiredCapacity} number of elements.
     * 
     * This method first tries to increase the size of the array by a factor of 1.5 to prevent a sequence of successive
     * increases by 1. It then evaluates the {@code nextCapacityHint} parameter as well as the {@code requiredCapacity}
     * parameter to determine the next size.
     *
     * @param length
     *         the current length of the array
     * @param requiredCapacity
     *         the immediately required capacity
     * @param nextCapacityHint
     *         a hint for future capacity requirements that may not be required as of now
     *
     * @return the size of an array that is guaranteed to hold {@code requiredCapacity} number of elements.
     */
    public static int computeNewCapacity(int length, int requiredCapacity, int nextCapacityHint) {
        if (requiredCapacity < length) {
            return length;
        }

        int newCapacity = (length * 3) / 2 + 1;

        if (newCapacity < nextCapacityHint) {
            newCapacity = nextCapacityHint;
        }

        if (newCapacity < requiredCapacity) {
            newCapacity = requiredCapacity;
        }

        return newCapacity;
    }
}