org.dmfs.rfc5545.recur.StaticUtils Maven / Gradle / Ivy

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/*
 * Copyright (C) 2013 Marten Gajda 
 *
 * 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 org.dmfs.rfc5545.recur;

import java.util.Arrays;
import java.util.List;


/**
 * A collection of static methods.
 *
 * @author Marten Gajda
 */
public final class StaticUtils
{

    /**
     * Convert a {@link List} of {@link Integer}s to a sorted array of ints.
     *
     * @param list
     *         The {@link List} to convert.
     *
     * @return an int[] or null if list is null.
     */
    public static int[] ListToSortedArray(List list)
    {
        if (list == null)
        {
            return null;
        }

        int count = list.size();
        int[] result = new int[count];
        int last = Integer.MIN_VALUE;
        boolean needsSorting = false;

        for (int i = 0; i < count; ++i)
        {
            int element = result[i] = list.get(i);
            needsSorting |= last > element;
            last = element;
        }
        if (needsSorting)
        {
            Arrays.sort(result);
        }
        return result;
    }


    /**
     * Convert a {@link List} of {@link Integer}s to an array of ints.
     *
     * @param list
     *         The {@link List} to convert.
     *
     * @return an int[] or null if list is null.
     */
    public static int[] ListToArray(List list)
    {
        if (list == null)
        {
            return null;
        }

        int count = list.size();
        int[] result = new int[count];

        for (int i = 0; i < count; ++i)
        {
            result[i] = list.get(i);
        }

        return result;
    }


    /**
     * Perform a linear search for an integer in a given array. For small fields a linear search can be faster than a binary search. So use this if you know
     * your field contains only few entries.
     *
     * @param array
     *         The array to search (the hay stack). Must not be null!
     * @param i
     *         The value to search for (the needle).
     *
     * @return the position of the value in the array or -1 if the value has not been found.
     */
    public static int linearSearch(int[] array, int i)
    {
        for (int c = 0, len = array.length; c < len; ++c)
        {
            if (array[c] == i)
            {
                return c;
            }
        }
        return -1;
    }


    /**
     * Perform a linear search for a long in a given array. For small fields a linear search can be faster than a binary search. So use this if you know your
     * field contains only few entries.
     *
     * @param array
     *         The array to search (the hay stack). Must not be null!
     * @param l
     *         The value to search for (the needle).
     *
     * @return the position of the value in the array or -1 if the value has not been found.
     */
    public static int linearSearch(long[] array, long l)
    {
        return linearSearch(array, 0, array.length, l);
    }


    /**
     * Perform a linear search for a long in a given array. For small fields a linear search can be faster than a binary search. So use this if you know your
     * field contains only few entries.
     *
     * @param array
     *         The array to search (the hay stack). Must not be null!
     * @param start
     *         the inclusive start position of the range to search
     * @param end
     *         the exclusive end position of the range to search
     * @param l
     *         The value to search for (the needle).
     *
     * @return the position of the value in the array or -1 if the value has not been found.
     */
    public static int linearSearch(long[] array, int start, int end, long l)
    {
        for (int c = start; c < end; ++c)
        {
            if (array[c] == l)
            {
                return c;
            }
        }
        return -1;
    }
}