Booleans
Date: 2016-05-24

com.google.common.primitives

## Class Booleans

- java.lang.Object
- - com.google.common.primitives.Booleans

-     @CheckReturnValue
      @GwtCompatible
      public final class Booleans
      extends java.lang.Object

  Static utility methods pertaining to `boolean` primitives, that are not already found in either `Boolean` or `Arrays`.

  See the Guava User Guide article on primitive utilities.

  Since:
    1.0

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `static java.util.List<java.lang.Boolean>` | `asList(boolean... backingArray)` Returns a fixed-size list backed by the specified array, similar to `Arrays.asList(Object[])`.
    `static int` | `compare(boolean a, boolean b)` Compares the two specified `boolean` values in the standard way (`false` is considered less than `true`).
    `static boolean[]` | `concat(boolean[]... arrays)` Returns the values from each provided array combined into a single array.
    `static boolean` | `contains(boolean[] array, boolean target)` Returns `true` if `target` is present as an element anywhere in `array`.
    `static int` | `countTrue(boolean... values)` Returns the number of `values` that are `true`.
    `static boolean[]` | `ensureCapacity(boolean[] array, int minLength, int padding)` Returns an array containing the same values as `array`, but guaranteed to be of a specified minimum length.
    `static int` | `hashCode(boolean value)` Returns a hash code for `value`; equal to the result of invoking `((Boolean) value).hashCode()`.
    `static int` | `indexOf(boolean[] array, boolean target)` Returns the index of the first appearance of the value `target` in `array`.
    `static int` | `indexOf(boolean[] array, boolean[] target)` Returns the start position of the first occurrence of the specified `target` within `array`, or `-1` if there is no such occurrence.
    `static java.lang.String` | `join(java.lang.String separator, boolean... array)` Returns a string containing the supplied `boolean` values separated by `separator`.
    `static int` | `lastIndexOf(boolean[] array, boolean target)` Returns the index of the last appearance of the value `target` in `array`.
    `static java.util.Comparator<boolean[]>` | `lexicographicalComparator()` Returns a comparator that compares two `boolean` arrays lexicographically.
    `static boolean[]` | `toArray(java.util.Collection<java.lang.Boolean> collection)` Copies a collection of `Boolean` instances into a new array of primitive `boolean` values.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Method Detail

    - #### hashCode

          public static int hashCode(boolean value)

      Returns a hash code for `value`; equal to the result of invoking `((Boolean) value).hashCode()`.
      Parameters:
        `value` - a primitive `boolean` value
      Returns:
        a hash code for the value

    - #### compare

          public static int compare(boolean a,
                    boolean b)

      Compares the two specified `boolean` values in the standard way (`false` is considered less than `true`). The sign of the value returned is the same as that of `((Boolean) a).compareTo(b)`.

      Note for Java 7 and later: this method should be treated as deprecated; use the equivalent `Boolean.compare(boolean, boolean)` method instead.

      Parameters:
        `a` - the first `boolean` to compare
        `b` - the second `boolean` to compare
      Returns:
        a positive number if only `a` is `true`, a negative number if only `b` is true, or zero if `a == b`

    - #### contains

          public static boolean contains(boolean[] array,
                         boolean target)

      Returns `true` if `target` is present as an element anywhere in `array`.

      Note: consider representing the array as a `BitSet` instead, replacing `Booleans.contains(array, true)` with `!bitSet.isEmpty()` and `Booleans.contains(array, false)` with `bitSet.nextClearBit(0) == sizeOfBitSet`.

      Parameters:
        `array` - an array of `boolean` values, possibly empty
        `target` - a primitive `boolean` value
      Returns:
        `true` if `array[i] == target` for some value of `i`

    - #### indexOf

          public static int indexOf(boolean[] array,
                    boolean target)

      Returns the index of the first appearance of the value `target` in `array`.

      Note: consider representing the array as a `BitSet` instead, and using `BitSet.nextSetBit(int)` or `BitSet.nextClearBit(int)`.

      Parameters:
        `array` - an array of `boolean` values, possibly empty
        `target` - a primitive `boolean` value
      Returns:
        the least index `i` for which `array[i] == target`, or `-1` if no such index exists.

    - #### indexOf

          public static int indexOf(boolean[] array,
                    boolean[] target)

      Returns the start position of the first occurrence of the specified `target` within `array`, or `-1` if there is no such occurrence.

      More formally, returns the lowest index `i` such that `java.util.Arrays.copyOfRange(array, i, i + target.length)` contains exactly the same elements as `target`.

      Parameters:
        `array` - the array to search for the sequence `target`
        `target` - the array to search for as a sub-sequence of `array`

    - #### lastIndexOf

          public static int lastIndexOf(boolean[] array,
                        boolean target)

      Returns the index of the last appearance of the value `target` in `array`.
      Parameters:
        `array` - an array of `boolean` values, possibly empty
        `target` - a primitive `boolean` value
      Returns:
        the greatest index `i` for which `array[i] == target`, or `-1` if no such index exists.

    - #### concat

          public static boolean[] concat(boolean[]... arrays)

      Returns the values from each provided array combined into a single array. For example, `concat(new boolean[] {a, b}, new boolean[] {}, new boolean[] {c}` returns the array `{a, b, c}`.
      Parameters:
        `arrays` - zero or more `boolean` arrays
      Returns:
        a single array containing all the values from the source arrays, in order

    - #### ensureCapacity

          public static boolean[] ensureCapacity(boolean[] array,
                                 int minLength,
                                 int padding)

      Returns an array containing the same values as `array`, but guaranteed to be of a specified minimum length. If `array` already has a length of at least `minLength`, it is returned directly. Otherwise, a new array of size `minLength + padding` is returned, containing the values of `array`, and zeroes in the remaining places.
      Parameters:
        `array` - the source array
        `minLength` - the minimum length the returned array must guarantee
        `padding` - an extra amount to "grow" the array by if growth is necessary
      Returns:
        an array containing the values of `array`, with guaranteed minimum length `minLength`
      Throws:
        `java.lang.IllegalArgumentException` - if `minLength` or `padding` is negative

    - #### join

          public static java.lang.String join(java.lang.String separator,
                              boolean... array)

      Returns a string containing the supplied `boolean` values separated by `separator`. For example, `join("-", false, true, false)` returns the string `"false-true-false"`.
      Parameters:
        `separator` - the text that should appear between consecutive values in the resulting string (but not at the start or end)
        `array` - an array of `boolean` values, possibly empty

    - #### lexicographicalComparator

          public static java.util.Comparator<boolean[]> lexicographicalComparator()

      Returns a comparator that compares two `boolean` arrays lexicographically. That is, it compares, using `compare(boolean, boolean)`), 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, `[] < [false] < [false, true] < [true]`.

      The returned comparator is inconsistent with `Object.equals(Object)` (since arrays support only identity equality), but it is consistent with `Arrays.equals(boolean[], boolean[])`.

      Since:
        2.0
      See Also:
        Lexicographical order article at Wikipedia

    - #### toArray

          public static boolean[] toArray(java.util.Collection<java.lang.Boolean> collection)

      Copies a collection of `Boolean` instances into a new array of primitive `boolean` values.

      Elements are copied from the argument collection as if by `collection.toArray()`. Calling this method is as thread-safe as calling that method.

      Note: consider representing the collection as a `BitSet` instead.

      Parameters:
        `collection` - a collection of `Boolean` objects
      Returns:
        an array containing the same values as `collection`, in the same order, converted to primitives
      Throws:
        `java.lang.NullPointerException` - if `collection` or any of its elements is null

    - #### asList

          public static java.util.List<java.lang.Boolean> asList(boolean... backingArray)

      Returns a fixed-size list backed by the specified array, similar to `Arrays.asList(Object[])`. The list supports `List.set(int, Object)`, but any attempt to set a value to `null` will result in a `NullPointerException`.

      The returned list maintains the values, but not the identities, of `Boolean` objects written to or read from it. For example, whether `list.get(0) == list.get(0)` is true for the returned list is unspecified.

      Parameters:
        `backingArray` - the array to back the list
      Returns:
        a list view of the array

    - #### countTrue

          @Beta
          public static int countTrue(boolean... values)

      Returns the number of `values` that are `true`.
      Since:
        16.0