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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 static final int BITS_PER_INT = 32;
27  
28      private Integers() {
29      }
30  
31      /**
32       * Parses the string argument as a signed decimal integer.
33       *
34       * @param s a {@code String} containing the {@code int} representation to parse, may be {@code null} or {@code ""}
35       * @param defaultValue 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 if the string does not contain a parsable integer.
38       */
39      public static int parseInt(final String s, final int defaultValue) {
40          return Strings.isEmpty(s) ? defaultValue : Integer.parseInt(s);
41      }
42  
43      /**
44       * Parses the string argument as a signed decimal integer.
45       *
46       * @param s a {@code String} containing the {@code int} representation to parse, may be {@code null} or {@code ""}
47       * @return the integer value represented by the argument in decimal.
48       * @throws NumberFormatException if the string does not contain a parsable integer.
49       */
50      public static int parseInt(final String s) {
51          return parseInt(s, 0);
52      }
53  
54      /**
55       * Calculate the next power of 2, greater than or equal to x.
56       * <p>
57       * From Hacker's Delight, Chapter 3, Harry S. Warren Jr.
58       *
59       * @param x Value to round up
60       * @return The next power of 2 from x inclusive
61       */
62      public static int ceilingNextPowerOfTwo(final int x) {
63          return 1 << (BITS_PER_INT - Integer.numberOfLeadingZeros(x - 1));
64      }
65  }