com.google.common.primitives
Class Booleans

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

public final class Booleans
extends Object

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

Since:

2009.09.15 tentative

Author:

Kevin Bourrillion

Method Summary

static List<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 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 String	join(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 Comparator<boolean[]>	lexicographicalComparator() Returns a comparator that compares two boolean arrays lexicographically.
static boolean[]	toArray(Collection<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).

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:

IllegalArgumentException - if minLength or padding is negative

join

public static String join(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 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:

2010.01.04 tentative

See Also:

Lexicographical order article at Wikipedia

toArray

public static boolean[] toArray(Collection<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:

NullPointerException - if collection or any of its elements is null

asList

public static List<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