001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017package org.apache.logging.log4j.core.util;
018
019import org.apache.logging.log4j.util.Strings;
020
021/**
022 * Helps deal with integers.
023 */
024public final class Integers {
025
026    private Integers() {
027    }
028
029    /**
030     * Parses the string argument as a signed decimal integer.
031     *
032     * @param s
033     *            a {@code String} containing the {@code int} representation to parse, may be {@code null} or {@code ""}
034     * @param defaultValue
035     *            the return value, use {@code defaultValue} if {@code s} is {@code null} or {@code ""}
036     * @return the integer value represented by the argument in decimal.
037     * @throws NumberFormatException
038     *             if the string does not contain a parsable integer.
039     */
040    public static int parseInt(final String s, final int defaultValue) {
041        return Strings.isEmpty(s) ? defaultValue : Integer.parseInt(s);
042    }
043
044    /**
045     * Parses the string argument as a signed decimal integer.
046     *
047     * @param s
048     *            a {@code String} containing the {@code int} representation to parse, may be {@code null} or {@code ""}
049     * @return the integer value represented by the argument in decimal.
050     * @throws NumberFormatException
051     *             if the string does not contain a parsable integer.
052     */
053    public static int parseInt(final String s) {
054        return parseInt(s, 0);
055    }
056    
057    /**
058     * Calculate the next power of 2, greater than or equal to x.<p>
059     * From Hacker's Delight, Chapter 3, Harry S. Warren Jr.
060     *
061     * @param x Value to round up
062     * @return The next power of 2 from x inclusive
063     */
064    public static int ceilingNextPowerOfTwo(final int x) {
065        return 1 << (32 - Integer.numberOfLeadingZeros(x - 1));
066    }
067}