https://github.com/google/guava/guava: Guava is a suite of core and expanded libraries that include utility classes, google's collections, io classes, and much much more. 
/*
 * Copyright (C) 2011 The Guava Authors
 *
 * 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 com.google.common.primitives;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkPositionIndexes;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.Arrays;
import java.util.Comparator;


Static utility methods pertaining to int primitives that interpret values as unsigned (that is, any negative value x is treated as the positive value 
2^32 + x). The methods for which signedness is not an issue are in Ints, as well as signed versions of methods for which signedness is an issue. 
In addition, this class provides several static methods for converting an int to a String and a String to an int that treat the int as an unsigned number. 
Users of these utilities must be extremely careful not to mix up signed and unsigned int values. When possible, it is recommended that the UnsignedInteger wrapper class be used, at a small efficiency penalty, to enforce the distinction in the type system. 
See the Guava User Guide article on unsigned
primitive utilities.

Author:Louis Wasserman
Since:11.0
/**
 * Static utility methods pertaining to {@code int} primitives that interpret values as
 * <i>unsigned</i> (that is, any negative value {@code x} is treated as the positive value {@code
 * 2^32 + x}). The methods for which signedness is not an issue are in {@link Ints}, as well as
 * signed versions of methods for which signedness is an issue.
 *
 * <p>In addition, this class provides several static methods for converting an {@code int} to a
 * {@code String} and a {@code String} to an {@code int} that treat the {@code int} as an unsigned
 * number.
 *
 * <p>Users of these utilities must be <i>extremely careful</i> not to mix up signed and unsigned
 * {@code int} values. When possible, it is recommended that the {@link UnsignedInteger} wrapper
 * class be used, at a small efficiency penalty, to enforce the distinction in the type system.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/PrimitivesExplained#unsigned-support">unsigned
 * primitive utilities</a>.
 *
 * @author Louis Wasserman
 * @since 11.0
 */
@Beta
@GwtCompatible
public final class UnsignedInts {
  static final long INT_MASK = 0xffffffffL;

  private UnsignedInts() {}

  static int flip(int value) {
    return value ^ Integer.MIN_VALUE;
  }

  
Compares the two specified int values, treating them as unsigned values between 
0 and 2^32 - 1 inclusive. 
Java 8 users: use Integer.compareUnsigned(int, int) instead. 
Params:
  • a – the first unsigned int to compare
  • b – the second unsigned int to compare
Returns:a negative value if a is less than b; a positive value if a is greater than b; or zero if they are equal
/**
   * Compares the two specified {@code int} values, treating them as unsigned values between {@code
   * 0} and {@code 2^32 - 1} inclusive.
   *
   * <p><b>Java 8 users:</b> use {@link Integer#compareUnsigned(int, int)} instead.
   *
   * @param a the first unsigned {@code int} to compare
   * @param b the second unsigned {@code int} to compare
   * @return a negative value if {@code a} is less than {@code b}; a positive value if {@code a} is
   *     greater than {@code b}; or zero if they are equal
   */
  public static int compare(int a, int b) {
    return Ints.compare(flip(a), flip(b));
  }

  
Returns the value of the given int as a long, when treated as unsigned. 
Java 8 users: use Integer.toUnsignedLong(int) instead. 
/**
   * Returns the value of the given {@code int} as a {@code long}, when treated as unsigned.
   *
   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedLong(int)} instead.
   */
  public static long toLong(int value) {
    return value & INT_MASK;
  }

  
Returns the int value that, when treated as unsigned, is equal to value, if possible. 
Params:
  • value – a value between 0 and 232-1 inclusive
Throws:
Returns:the int value that, when treated as unsigned, equals value
Since:21.0
/**
   * Returns the {@code int} value that, when treated as unsigned, is equal to {@code value}, if
   * possible.
   *
   * @param value a value between 0 and 2<sup>32</sup>-1 inclusive
   * @return the {@code int} value that, when treated as unsigned, equals {@code value}
   * @throws IllegalArgumentException if {@code value} is negative or greater than or equal to
   *     2<sup>32</sup>
   * @since 21.0
   */
  public static int checkedCast(long value) {
    checkArgument((value >> Integer.SIZE) == 0, "out of range: %s", value);
    return (int) value;
  }

  
Returns the int value that, when treated as unsigned, is nearest in value to 
value. 
Params:
  • value – any long value
Returns:2^32 - 1 if value >= 2^32, 0 if value <= 0, and 
    value cast to int otherwise
Since:21.0
/**
   * Returns the {@code int} value that, when treated as unsigned, is nearest in value to {@code
   * value}.
   *
   * @param value any {@code long} value
   * @return {@code 2^32 - 1} if {@code value >= 2^32}, {@code 0} if {@code value <= 0}, and {@code
   *     value} cast to {@code int} otherwise
   * @since 21.0
   */
  public static int saturatedCast(long value) {
    if (value <= 0) {
      return 0;
    } else if (value >= (1L << 32)) {
      return -1;
    } else {
      return (int) value;
    }
  }

  
Returns the least value present in array, treating values as unsigned. 
Params:
  • array – a nonempty array of unsigned int values
Throws:
Returns:the value present in array that is less than or equal to every other value in the array according to compare
/**
   * Returns the least value present in {@code array}, treating values as unsigned.
   *
   * @param array a <i>nonempty</i> array of unsigned {@code int} values
   * @return the value present in {@code array} that is less than or equal to every other value in
   *     the array according to {@link #compare}
   * @throws IllegalArgumentException if {@code array} is empty
   */
  public static int min(int... array) {
    checkArgument(array.length > 0);
    int min = flip(array[0]);
    for (int i = 1; i < array.length; i++) {
      int next = flip(array[i]);
      if (next < min) {
        min = next;
      }
    }
    return flip(min);
  }

  
Returns the greatest value present in array, treating values as unsigned. 
Params:
  • array – a nonempty array of unsigned int values
Throws:
Returns:the value present in array that is greater than or equal to every other value in the array according to compare
/**
   * Returns the greatest value present in {@code array}, treating values as unsigned.
   *
   * @param array a <i>nonempty</i> array of unsigned {@code int} values
   * @return the value present in {@code array} that is greater than or equal to every other value
   *     in the array according to {@link #compare}
   * @throws IllegalArgumentException if {@code array} is empty
   */
  public static int max(int... array) {
    checkArgument(array.length > 0);
    int max = flip(array[0]);
    for (int i = 1; i < array.length; i++) {
      int next = flip(array[i]);
      if (next > max) {
        max = next;
      }
    }
    return flip(max);
  }

  
Returns a string containing the supplied unsigned int values separated by 
separator. For example, join("-", 1, 2, 3) returns the string "1-2-3". 
Params:
  • separator – the text that should appear between consecutive values in the resulting string
    (but not at the start or end)
  • array – an array of unsigned int values, possibly empty
/**
   * Returns a string containing the supplied unsigned {@code int} values separated by {@code
   * separator}. For example, {@code join("-", 1, 2, 3)} returns the string {@code "1-2-3"}.
   *
   * @param separator the text that should appear between consecutive values in the resulting string
   *     (but not at the start or end)
   * @param array an array of unsigned {@code int} values, possibly empty
   */
  public static String join(String separator, int... array) {
    checkNotNull(separator);
    if (array.length == 0) {
      return "";
    }

    // For pre-sizing a builder, just get the right order of magnitude
    StringBuilder builder = new StringBuilder(array.length * 5);
    builder.append(toString(array[0]));
    for (int i = 1; i < array.length; i++) {
      builder.append(separator).append(toString(array[i]));
    }
    return builder.toString();
  }

  
Returns a comparator that compares two arrays of unsigned int values lexicographically. That is, it compares, using compare(int, int)), the first pair of values that follow any common prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For example, [] < [1] < [1, 2] < [2] < [1 << 31]. 
The returned comparator is inconsistent with Object.equals(Object) (since arrays support only identity equality), but it is consistent with Arrays.equals(int[], int[]). 
/**
   * Returns a comparator that compares two arrays of unsigned {@code int} values <a
   * href="http://en.wikipedia.org/wiki/Lexicographical_order">lexicographically</a>. That is, it
   * compares, using {@link #compare(int, int)}), the first pair of values that follow any common
   * prefix, or when one array is a prefix of the other, treats the shorter array as the lesser. For
   * example, {@code [] < [1] < [1, 2] < [2] < [1 << 31]}.
   *
   * <p>The returned comparator is inconsistent with {@link Object#equals(Object)} (since arrays
   * support only identity equality), but it is consistent with {@link Arrays#equals(int[], int[])}.
   */
  public static Comparator<int[]> lexicographicalComparator() {
    return LexicographicalComparator.INSTANCE;
  }

  enum LexicographicalComparator implements Comparator<int[]> {
    INSTANCE;

    @Override
    public int compare(int[] left, int[] right) {
      int minLength = Math.min(left.length, right.length);
      for (int i = 0; i < minLength; i++) {
        if (left[i] != right[i]) {
          return UnsignedInts.compare(left[i], right[i]);
        }
      }
      return left.length - right.length;
    }

    @Override
    public String toString() {
      return "UnsignedInts.lexicographicalComparator()";
    }
  }

  
Sorts the array, treating its elements as unsigned 32-bit integers.

Since:23.1
/**
   * Sorts the array, treating its elements as unsigned 32-bit integers.
   *
   * @since 23.1
   */
  public static void sort(int[] array) {
    checkNotNull(array);
    sort(array, 0, array.length);
  }

  
Sorts the array between fromIndex inclusive and toIndex exclusive, treating its elements as unsigned 32-bit integers. 
Since:23.1
/**
   * Sorts the array between {@code fromIndex} inclusive and {@code toIndex} exclusive, treating its
   * elements as unsigned 32-bit integers.
   *
   * @since 23.1
   */
  public static void sort(int[] array, int fromIndex, int toIndex) {
    checkNotNull(array);
    checkPositionIndexes(fromIndex, toIndex, array.length);
    for (int i = fromIndex; i < toIndex; i++) {
      array[i] = flip(array[i]);
    }
    Arrays.sort(array, fromIndex, toIndex);
    for (int i = fromIndex; i < toIndex; i++) {
      array[i] = flip(array[i]);
    }
  }

  
Sorts the elements of array in descending order, interpreting them as unsigned 32-bit integers. 
Since:23.1
/**
   * Sorts the elements of {@code array} in descending order, interpreting them as unsigned 32-bit
   * integers.
   *
   * @since 23.1
   */
  public static void sortDescending(int[] array) {
    checkNotNull(array);
    sortDescending(array, 0, array.length);
  }

  
Sorts the elements of array between fromIndex inclusive and toIndex exclusive in descending order, interpreting them as unsigned 32-bit integers. 
Since:23.1
/**
   * Sorts the elements of {@code array} between {@code fromIndex} inclusive and {@code toIndex}
   * exclusive in descending order, interpreting them as unsigned 32-bit integers.
   *
   * @since 23.1
   */
  public static void sortDescending(int[] array, int fromIndex, int toIndex) {
    checkNotNull(array);
    checkPositionIndexes(fromIndex, toIndex, array.length);
    for (int i = fromIndex; i < toIndex; i++) {
      array[i] ^= Integer.MAX_VALUE;
    }
    Arrays.sort(array, fromIndex, toIndex);
    for (int i = fromIndex; i < toIndex; i++) {
      array[i] ^= Integer.MAX_VALUE;
    }
  }

  
Returns dividend / divisor, where the dividend and divisor are treated as unsigned 32-bit
quantities.

Java 8 users: use Integer.divideUnsigned(int, int) instead. 
Params:
  • dividend – the dividend (numerator)
  • divisor – the divisor (denominator)
Throws:
/**
   * Returns dividend / divisor, where the dividend and divisor are treated as unsigned 32-bit
   * quantities.
   *
   * <p><b>Java 8 users:</b> use {@link Integer#divideUnsigned(int, int)} instead.
   *
   * @param dividend the dividend (numerator)
   * @param divisor the divisor (denominator)
   * @throws ArithmeticException if divisor is 0
   */
  public static int divide(int dividend, int divisor) {
    return (int) (toLong(dividend) / toLong(divisor));
  }

  
Returns dividend % divisor, where the dividend and divisor are treated as unsigned 32-bit
quantities.

Java 8 users: use Integer.remainderUnsigned(int, int) instead. 
Params:
  • dividend – the dividend (numerator)
  • divisor – the divisor (denominator)
Throws:
/**
   * Returns dividend % divisor, where the dividend and divisor are treated as unsigned 32-bit
   * quantities.
   *
   * <p><b>Java 8 users:</b> use {@link Integer#remainderUnsigned(int, int)} instead.
   *
   * @param dividend the dividend (numerator)
   * @param divisor the divisor (denominator)
   * @throws ArithmeticException if divisor is 0
   */
  public static int remainder(int dividend, int divisor) {
    return (int) (toLong(dividend) % toLong(divisor));
  }

  
Returns the unsigned int value represented by the given string. 
Accepts a decimal, hexadecimal, or octal number given by specifying the following prefix:

    
  
  • 0xHexDigits
  
  • 0XHexDigits
  
  • #HexDigits
  
  • 0OctalDigits



Throws:
Since:13.0
/**
   * Returns the unsigned {@code int} value represented by the given string.
   *
   * <p>Accepts a decimal, hexadecimal, or octal number given by specifying the following prefix:
   *
   * <ul>
   *   <li>{@code 0x}<i>HexDigits</i>
   *   <li>{@code 0X}<i>HexDigits</i>
   *   <li>{@code #}<i>HexDigits</i>
   *   <li>{@code 0}<i>OctalDigits</i>
   * </ul>
   *
   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
   * @since 13.0
   */
  @CanIgnoreReturnValue
  public static int decode(String stringValue) {
    ParseRequest request = ParseRequest.fromString(stringValue);

    try {
      return parseUnsignedInt(request.rawValue, request.radix);
    } catch (NumberFormatException e) {
      NumberFormatException decodeException =
          new NumberFormatException("Error parsing value: " + stringValue);
      decodeException.initCause(e);
      throw decodeException;
    }
  }

  
Returns the unsigned int value represented by the given decimal string. 
Java 8 users: use Integer.parseUnsignedInt(String) instead. 
Throws:
/**
   * Returns the unsigned {@code int} value represented by the given decimal string.
   *
   * <p><b>Java 8 users:</b> use {@link Integer#parseUnsignedInt(String)} instead.
   *
   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int} value
   * @throws NullPointerException if {@code s} is null (in contrast to {@link
   *     Integer#parseInt(String)})
   */
  @CanIgnoreReturnValue
  public static int parseUnsignedInt(String s) {
    return parseUnsignedInt(s, 10);
  }

  
Returns the unsigned int value represented by a string with the given radix. 
Java 8 users: use Integer.parseUnsignedInt(String, int) instead. 
Params:
Throws:
/**
   * Returns the unsigned {@code int} value represented by a string with the given radix.
   *
   * <p><b>Java 8 users:</b> use {@link Integer#parseUnsignedInt(String, int)} instead.
   *
   * @param string the string containing the unsigned integer representation to be parsed.
   * @param radix the radix to use while parsing {@code s}; must be between {@link
   *     Character#MIN_RADIX} and {@link Character#MAX_RADIX}.
   * @throws NumberFormatException if the string does not contain a valid unsigned {@code int}, or
   *     if supplied radix is invalid.
   * @throws NullPointerException if {@code s} is null (in contrast to {@link
   *     Integer#parseInt(String)})
   */
  @CanIgnoreReturnValue
  public static int parseUnsignedInt(String string, int radix) {
    checkNotNull(string);
    long result = Long.parseLong(string, radix);
    if ((result & INT_MASK) != result) {
      throw new NumberFormatException(
          "Input " + string + " in base " + radix + " is not in the range of an unsigned integer");
    }
    return (int) result;
  }

  
Returns a string representation of x, where x is treated as unsigned.

Java 8 users: use Integer.toUnsignedString(int) instead. 
/**
   * Returns a string representation of x, where x is treated as unsigned.
   *
   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedString(int)} instead.
   */
  public static String toString(int x) {
    return toString(x, 10);
  }

  
Returns a string representation of x for the given radix, where x is treated as unsigned. 
Java 8 users: use Integer.toUnsignedString(int, int) instead. 
Params:
  • x – the value to convert to a string.
  • radix – the radix to use while working with x
Throws:
/**
   * Returns a string representation of {@code x} for the given radix, where {@code x} is treated as
   * unsigned.
   *
   * <p><b>Java 8 users:</b> use {@link Integer#toUnsignedString(int, int)} instead.
   *
   * @param x the value to convert to a string.
   * @param radix the radix to use while working with {@code x}
   * @throws IllegalArgumentException if {@code radix} is not between {@link Character#MIN_RADIX}
   *     and {@link Character#MAX_RADIX}.
   */
  public static String toString(int x, int radix) {
    long asLong = x & INT_MASK;
    return Long.toString(asLong, radix);
  }
}