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    1   /*
    2    * Licensed to the Apache Software Foundation (ASF) under one or more
    3    * contributor license agreements. See the NOTICE file distributed with
    4    * this work for additional information regarding copyright ownership.
    5    * The ASF licenses this file to You under the Apache license, Version 2.0
    6    * (the "License"); you may not use this file except in compliance with
    7    * the License. You may obtain a copy of the License at
    8    *
    9    *      http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the license for the specific language governing permissions and
    15   * limitations under the license.
    16   */
    17  package org.apache.logging.log4j.core.util;
    18
    19  import org.apache.logging.log4j.util.Strings;
    20
    21  /**
    22   * Helps deal with integers.
    23   */
    24  public final class Integers {
    25
    26      private Integers() {
    27      }
    28
    29      /**
    30       * Parses the string argument as a signed decimal integer.
    31       *
    32       * @param s
    33       *            a {@code String} containing the {@code int} representation to parse, may be {@code null} or {@code ""}
    34       * @param defaultValue
    35       *            the return value, use {@code defaultValue} if {@code s} is {@code null} or {@code ""}
    36       * @return the integer value represented by the argument in decimal.
    37       * @throws NumberFormatException
    38       *             if the string does not contain a parsable integer.
    39       */
    40      public static int parseInt(final String s, final int defaultValue) {
    41          return Strings.isEmpty(s) ? defaultValue : Integer.parseInt(s);
    42      }
    43
    44      /**
    45       * Parses the string argument as a signed decimal integer.
    46       *
    47       * @param s
    48       *            a {@code String} containing the {@code int} representation to parse, may be {@code null} or {@code ""}
    49       * @return the integer value represented by the argument in decimal.
    50       * @throws NumberFormatException
    51       *             if the string does not contain a parsable integer.
    52       */
    53      public static int parseInt(final String s) {
    54          return parseInt(s, 0);
    55      }
    56
    57      /**
    58       * Calculate the next power of 2, greater than or equal to x.<p>
    59       * From Hacker's Delight, Chapter 3, Harry S. Warren Jr.
    60       *
    61       * @param x Value to round up
    62       * @return The next power of 2 from x inclusive
    63       */
    64      public static int ceilingNextPowerOfTwo(final int x) {
    65          return 1 << (32 - Integer.numberOfLeadingZeros(x - 1));
    66      }
    67  }