com.google.common.primitives
Class Doubles

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

public final class Doubles
extends Object

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

Since:

2009.09.15 tentative

Author:

Kevin Bourrillion

Method Summary

static List<Double>	asList(double... backingArray) Returns a fixed-size list backed by the specified array, similar to Arrays.asList(Object[]).
static int	compare(double a, double b) Compares the two specified double values.
static double[]	concat(double[]... arrays) Returns the values from each provided array combined into a single array.
static boolean	contains(double[] array, double target) Returns true if target is present as an element anywhere in array.
static double[]	ensureCapacity(double[] 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(double value) Returns a hash code for value; equal to the result of invoking ((Double) value).hashCode().
static int	indexOf(double[] array, double target) Returns the index of the first appearance of the value target in array.
static int	indexOf(double[] array, double[] 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, double... array) Returns a string containing the supplied double values, converted to strings as specified by Double.toString(double), and separated by separator.
static int	lastIndexOf(double[] array, double target) Returns the index of the last appearance of the value target in array.
static Comparator<double[]>	lexicographicalComparator() Returns a comparator that compares two double arrays lexicographically.
static double	max(double... array) Returns the greatest value present in array, using the same rules of comparison as Math.max(double, double).
static double	min(double... array) Returns the least value present in array, using the same rules of comparison as Math.min(double, double).
static double[]	toArray(Collection<Double> collection) Copies a collection of Double instances into a new array of primitive double 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(double value)

Returns a hash code for value; equal to the result of invoking ((Double) value).hashCode().

Parameters:

value - a primitive double value

Returns:

a hash code for the value

compare

public static int compare(double a,
                          double b)

Compares the two specified double values. The sign of the value returned is the same as that of ((Double) a).compareTo(b). As with that method, NaN is treated as greater than all other values, and 0.0 > -0.0.

Parameters:

a - the first double to compare

b - the second double 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

contains

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

Returns true if target is present as an element anywhere in array. Note that this always returns false when target is NaN.

Parameters:

array - an array of double values, possibly empty

target - a primitive double value

Returns:

true if array[i] == target for some value of i

indexOf

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

Returns the index of the first appearance of the value target in array. Note that this always returns -1 when target is NaN.

Parameters:

array - an array of double values, possibly empty

target - a primitive double value

Returns:

the least index i for which array[i] == target, or -1 if no such index exists.

indexOf

public static int indexOf(double[] array,
                          double[] 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.

Note that this always returns -1 when target contains NaN.

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(double[] array,
                              double target)

Returns the index of the last appearance of the value target in array. Note that this always returns -1 when target is NaN.

Parameters:

array - an array of double values, possibly empty

target - a primitive double value

Returns:

the greatest index i for which array[i] == target, or -1 if no such index exists.

min

public static double min(double... array)

Returns the least value present in array, using the same rules of comparison as Math.min(double, double).

Parameters:

array - a nonempty array of double values

Returns:

the value present in array that is less than or equal to every other value in the array

Throws:

IllegalArgumentException - if array is empty

max

public static double max(double... array)

Returns the greatest value present in array, using the same rules of comparison as Math.max(double, double).

Parameters:

array - a nonempty array of double values

Returns:

the value present in array that is greater than or equal to every other value in the array

Throws:

IllegalArgumentException - if array is empty

concat

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

Returns the values from each provided array combined into a single array. For example, concat(new double[] {a, b}, new double[] {}, new double[] {c} returns the array {a, b, c}.

Parameters:

arrays - zero or more double arrays

Returns:

a single array containing all the values from the source arrays, in order

ensureCapacity

public static double[] ensureCapacity(double[] 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,
                          double... array)

Returns a string containing the supplied double values, converted to strings as specified by Double.toString(double), and separated by separator. For example, join("-", 1.0, 2.0, 3.0) returns the string "1.0-2.0-3.0".

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 double values, possibly empty

lexicographicalComparator

public static Comparator<double[]> lexicographicalComparator()

Returns a comparator that compares two double arrays lexicographically. That is, it compares, using compare(double, double)), 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, [] < [1.0] < [1.0, 2.0] < [2.0].

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

Since:

2010.01.04 tentative

See Also:

Lexicographical order article at Wikipedia

toArray

public static double[] toArray(Collection<Double> collection)

Copies a collection of Double instances into a new array of primitive double values.

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

Parameters:

collection - a collection of Double 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<Double> asList(double... 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 Double objects written to or read from it. For example, whether list.get(0) == list.get(0) is true for the returned list is unspecified.

The returned list may have unexpected behavior if it contains NaN, or if NaN is used as a parameter to any of its methods.

Parameters:

backingArray - the array to back the list

Returns:

a list view of the array