    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     */
    017    package org.apache.logging.log4j.core.util;
    018
    019    import org.apache.logging.log4j.util.Strings;
    020
    021    /**
    022     * Helps deal with integers.
    023     */
    024    public 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    }