Package org.kiwiproject.collect

Class KiwiArrays

java.lang.Object

org.kiwiproject.collect.KiwiArrays

public class KiwiArrays
extends Object

Utility methods for working with Array instances.

Constructor Summary

Constructors

Constructor	Description
KiwiArrays()

Method Summary

Modifier and Type	Method	Description
static <T> void	checkMinimumSize(T[] items, int minSize)	Checks that the given array is not null and has the given minimum size.
static <T> void	checkNonNullInputArray(T[] items)	Checks that the given array is not null.
static <T> T[]	distinct(T[] collection, Class<T> arrayType)	Returns a array of the collection elements with duplicates stripped out.
static <T> T[]	distinctOrNull(T[] collection, Class<T> arrayType)	Returns a array of the collection elements with duplicates stripped out or `null` if a null value is passed in.
static <T> T	fifth(T[] items)	Return the fifth element in the specified array of items.
static <T> T	first(T[] items)	Return the first element in the specified array of items.
static <T> Optional<T>	firstIfPresent(T[] items)	Returns an Optional containing the first element in specified array of items, or an empty optional if the array is null or empty.
static <T> T[]	firstN(T[] items, int number)	Returns a new array containing the "first N" elements of the input array.
static <T> T	fourth(T[] items)	Return the fourth element in the specified array of items.
static <T> boolean	hasOneElement(T[] items)	Checks whether the specified array is non-null and has only one item.
static <T> boolean	isNotNullOrEmpty(T[] items)	Checks whether the specified array is neither null nor empty.
static <T> boolean	isNullOrEmpty(T[] items)	Checks whether the specified array is null or empty.
static <T> T	last(T[] items)	Returns the last element in the specified array of items.
static <T> Optional<T>	lastIfPresent(T[] items)	Returns an Optional containing the last element in specified array of items, or an empty optional if the array is null or empty.
static <T> T[]	lastN(T[] items, int number)	Returns a new array containing the "last N" elements of the input array.
static <T> T[]	newArrayStartingAtCircularOffset(T[] input, long startOffset, Class<T> arrayType)	Returns a new array with the same elements and the same size as the original, however the initial position in the array is now the element specified by the "startOffset" and the array wraps around through the contents to end with "startOffset" - 1
static <T> T	nth(T[] items, int number)	Return the nth element in the specified array of items, starting at one for the first element, two for the second, etc.
static <T> T	penultimate(T[] items)	Returns the penultimate (second to last) element in the specified array.
static <T> T	second(T[] items)	Return the second element in the specified array of items.
static <T> T	secondToLast(T[] items)	Synonym for penultimate(Object[]).
static <T> T[]	sorted(T[] items, Class<T> arrayType)	Given an array, sort it according to the natural order, returning a new list.
static <T> T[]	sorted(T[] items, Comparator<T> comparator, Class<T> arrayType)	Given an array, sort it according to the provided Comparator returning a new array.
static <T> T[]	subArrayExcludingFirst(T[] items)	Returns a new array containing the portion of the given array excluding the first element.
static <T> T[]	subArrayExcludingLast(T[] items)	Returns a new array containing the portion of the given array excluding the last element.
static <T> T[]	subArrayFrom(T[] items, int number)	Returns a new array containing the portion of the given array starting at the given logical element number, where the numbers start at one, until and including the last element in the array.
static <T> T[]	subArrayFromIndex(T[] items, int index)	Returns a new array containing the portion of the given array starting at the given index, until and including the last element in the array.
static <T> T	third(T[] items)	Return the third element in the specified array of items.

Methods inherited from class java.lang.Object

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

Constructor Detail

KiwiArrays

public KiwiArrays()

Method Detail

isNullOrEmpty

public static <T> boolean isNullOrEmpty(T[] items)

Checks whether the specified array is null or empty.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

true if array is null or empty; false otherwise

isNotNullOrEmpty

public static <T> boolean isNotNullOrEmpty(T[] items)

Checks whether the specified array is neither null nor empty.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

true if array is NOT null or empty; false otherwise

hasOneElement

public static <T> boolean hasOneElement(T[] items)

Checks whether the specified array is non-null and has only one item.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

true if array is non-null and has exactly one item; false otherwise

sorted

public static <T> T[] sorted(T[] items,
                             Class<T> arrayType)

Given an array, sort it according to the natural order, returning a new list.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

arrayType - the type of the items in the array. Needed to ensure the new array is not Object[]

Returns:

a new sorted array

sorted

public static <T> T[] sorted(T[] items,
                             Comparator<T> comparator,
                             Class<T> arrayType)

Given an array, sort it according to the provided Comparator returning a new array.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

comparator - a Comparator to be used to compare stream elements

arrayType - the type of the items in the array. Needed to ensure the new array is not Object[]

Returns:

a new sorted array

first

public static <T> T first(T[] items)

Return the first element in the specified array of items.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

the first item in items

Throws:

IllegalArgumentException - if the array does not contain at least one item

NullPointerException - if the array is null

firstIfPresent

public static <T> Optional<T> firstIfPresent(T[] items)

Returns an Optional containing the first element in specified array of items, or an empty optional if the array is null or empty.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

Optional containing first element if exists, otherwise Optional.empty()

second

public static <T> T second(T[] items)

Return the second element in the specified array of items.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

the second item in items

Throws:

IllegalArgumentException - if the array does not contain at least two items

NullPointerException - if the array is null

third

public static <T> T third(T[] items)

Return the third element in the specified array of items.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

the third item in items

Throws:

IllegalArgumentException - if the array does not contain at least three items

NullPointerException - if the array is null

fourth

public static <T> T fourth(T[] items)

Return the fourth element in the specified array of items.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

the fourth item in items

Throws:

IllegalArgumentException - if the array does not contain at least four items

NullPointerException - if the array is null

fifth

public static <T> T fifth(T[] items)

Return the fifth element in the specified array of items.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

the fifth item in items

Throws:

IllegalArgumentException - if the array does not contain at least five items

NullPointerException - if the array is null

penultimate

public static <T> T penultimate(T[] items)

Returns the penultimate (second to last) element in the specified array.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

the penultimate item in items

Throws:

IllegalArgumentException - if the array does not contain at least two items

NullPointerException - if the array is null

See Also:

secondToLast(Object[])

secondToLast

public static <T> T secondToLast(T[] items)

Synonym for penultimate(Object[]).

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

the penultimate item in items

Throws:

IllegalArgumentException - if the array does not contain at least two items

NullPointerException - if the array is null

See Also:

penultimate(Object[])

last

public static <T> T last(T[] items)

Returns the last element in the specified array of items.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

the last item in the list

Throws:

IllegalArgumentException - if the array does not contain at least one item

NullPointerException - if the array is null

lastIfPresent

public static <T> Optional<T> lastIfPresent(T[] items)

Returns an Optional containing the last element in specified array of items, or an empty optional if the array is null or empty.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Returns:

Optional containing last element if exists, otherwise Optional.empty()

nth

public static <T> T nth(T[] items,
                        int number)

Return the nth element in the specified array of items, starting at one for the first element, two for the second, etc.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

number - the number of the element to retrieve, starting at one (not zero)

Returns:

the nth item in items

Throws:

IllegalArgumentException - if the array does not contain at least number items

NullPointerException - if the array is null

distinct

public static <T> T[] distinct(T[] collection,
                               Class<T> arrayType)

Returns a array of the collection elements with duplicates stripped out.

Type Parameters:

T - the type of items in the collection

Parameters:

collection - the collection of values

arrayType - the type of the items in the array. Needed to ensure the new array is not Object[]

Returns:

a new array with only unique elements

Throws:

IllegalArgumentException - if the collection is null

distinctOrNull

public static <T> T[] distinctOrNull(T[] collection,
                                     Class<T> arrayType)

Returns a array of the collection elements with duplicates stripped out or `null` if a null value is passed in.

Type Parameters:

T - the type of items in the collection

Parameters:

collection - the collection of values

arrayType - the type of the items in the array. Needed to ensure the new array is not Object[]

Returns:

a new array with only unique elements or null.

newArrayStartingAtCircularOffset

public static <T> T[] newArrayStartingAtCircularOffset(T[] input,
                                                       long startOffset,
                                                       Class<T> arrayType)

Returns a new array with the same elements and the same size as the original, however the initial position in the array is now the element specified by the "startOffset" and the array wraps around through the contents to end with "startOffset" - 1

Type Parameters:

T - the type of the items in the array

Parameters:

input - the original array

startOffset - the desired offset to start the new array

arrayType - the type of the items in the array. Needed to ensure the new array is not Object[]

Returns:

a new array starting at the desired offset

subArrayExcludingFirst

public static <T> T[] subArrayExcludingFirst(T[] items)

Returns a new array containing the portion of the given array excluding the first element.

Type Parameters:

T - the type of the items in the array

Parameters:

items - the array

Returns:

a new array containing the given array excluding the first item

Throws:

NullPointerException - if the array is null

subArrayExcludingLast

public static <T> T[] subArrayExcludingLast(T[] items)

Returns a new array containing the portion of the given array excluding the last element.

Type Parameters:

T - the type of the items in the array

Parameters:

items - the array

Returns:

a new array containing the given array excluding the last item

Throws:

NullPointerException - if the array is null

subArrayFrom

public static <T> T[] subArrayFrom(T[] items,
                                   int number)

Returns a new array containing the portion of the given array starting at the given logical element number, where the numbers start at one, until and including the last element in the array. This is useful if something is using one-based element numbers for some reason. Use subArrayFromIndex(Object[], int) if you want to use zero-based list indices.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

number - the number of the element to start the subarray, starting at one (not zero)

Returns:

a new array containing the given array, starting at the given one-based number

Throws:

NullPointerException - if the array is null

IllegalArgumentException - if the given number is negative or is higher than the size of the array

subArrayFromIndex

public static <T> T[] subArrayFromIndex(T[] items,
                                        int index)

Returns a new array containing the portion of the given array starting at the given index, until and including the last element in the array.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

index - the index in the array to start the subarray, zero-based like normal Array accessors

Returns:

a new array containing the given array, starting at the given zero-based index

Throws:

NullPointerException - if the array is null

IllegalArgumentException - if the given index is negative or is higher than the last index in the array

firstN

public static <T> T[] firstN(T[] items,
                             int number)

Returns a new array containing the "first N" elements of the input array.

If the given number is larger than the size of the array, the entire array is returned, rather than throw an exception. In this case, the input array is returned directly, i.e. return items.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

number - the number of items wanted from the start of the array

Returns:

a new array containing the given array containing the last number elements

lastN

public static <T> T[] lastN(T[] items,
                            int number)

Returns a new array containing the "last N" elements of the input array.

If the given number is larger than the size of the array, the entire array is returned, rather than throw an exception. In this case, the input array is returned directly, i.e. return items.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

number - the number of items wanted from the end of the array

Returns:

a new array containing the given array containing the first number elements

checkMinimumSize

public static <T> void checkMinimumSize(T[] items,
                                        int minSize)

Checks that the given array is not null and has the given minimum size.

Type Parameters:

T - the type of the items in the array

Parameters:

items - the array

minSize - the minimum required size

Throws:

NullPointerException - if the array is null

IllegalArgumentException - if minSize is not positive or the array does not contain minSize elements

checkNonNullInputArray

public static <T> void checkNonNullInputArray(T[] items)

Checks that the given array is not null.

Type Parameters:

T - the type of items in the array

Parameters:

items - the array

Throws:

NullPointerException - if the array is null