Package evo.search.util

Class ListUtils

java.lang.Object

evo.search.util.ListUtils

public class ListUtils
extends Object

List utility methods.

Field Summary

Fields

Modifier and Type	Field	Description
static BinaryOperator<String>	REDUCE_WITH_SPACE	Reduce function to connect two strings via a space character.

Constructor Summary

Constructors

Constructor	Description
ListUtils()

Method Summary

Modifier and Type	Method	Description
static <T> T	chooseRandom(List<T> list)	Choose a random item from the given list.
static <T> T	chooseRandom(List<T> list, int min, int max)	Choose a random item from the given list in the index range between min and max.
static <T> void	consec(List<T> list, BiConsumer<T,T> consumer)	Look at a list of consecutive items in pairs of two.
static <T,R> List<R>	consecMap(List<T> list, BiFunction<T,T,R> mapping)	Map a list of consecutive items in pairs of two to a new list.
static <T> double	consecSum(List<T> list, BiFunction<T,T,Double> mapper)	Consecutively compute a sum over each pair of the list.
static <T> List<T>	deepClone(List<T> items, UnaryOperator<T> cloner)	Deep clone a list of items.
static <T> List<T>	from(Iterator<T> iterator)	Generate a list from an iterator.
static <T> List<T>	generate(int limit, Supplier<T> supplier)	Generate a List with a given length through a supplier.
static float	getMinMaxRatio(float[] distances)	Compute the ratio of the maximum value divided by the minimum value of the float array.
static <T,R> List<R>	map(List<T> list, Function<T,R> mapper)	List mapping.
static double	mean(List<Double> numbers)	Computes the mean value of the list of doubles.
static <T> String	printConsecutive(List<T> list, Function<T,String> mapper, String separator)	Prints list of objects in a consecutive order.
static <T> T	reduce(List<T> list, BinaryOperator<T> reducer, T optional)	Reduce a list of items to a single item.
static <T> List<T>	removeRepeating(List<T> list)	Remove repeating elements from a list.
static BinaryOperator<String>	separator(String separator)	Returns a binary string reducing operator concatenating a collection of strings with a given separator.
static double	sum(List<? extends Number> numbers)	Calculate the sum of the list of doubles.
static <T> List<List<T>>	transpose(List<List<T>> matrix)	Transpose a two dimensional list matrix.
static double	variance(List<? extends Number> list)	Calculates the variance for a list of numbers.

Methods inherited from class java.lang.Object

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

Field Detail

REDUCE_WITH_SPACE

public static final BinaryOperator<String> REDUCE_WITH_SPACE

Reduce function to connect two strings via a space character.

Constructor Detail

ListUtils

public ListUtils()

Method Detail

separator

public static BinaryOperator<String> separator(String separator)

Returns a binary string reducing operator concatenating a collection of strings with a given separator.

Parameters:

separator - separator to place between each pair of strings

Returns:

concatenated string of the collection's string separated by the given separator

generate

public static <T> List<T> generate(int limit,
                                   Supplier<T> supplier)

Generate a List with a given length through a supplier.

Type Parameters:

T - list/supplier item type

Parameters:

limit - length of the new list

supplier - supplier to retrieve the items from

Returns:

a list with element generated by the given supplier

chooseRandom

public static <T> T chooseRandom(List<T> list,
                                 int min,
                                 int max)

Choose a random item from the given list in the index range between min and max.

Type Parameters:

T - list element and return type

Parameters:

list - list to choose from

min - minimum index

max - maximum index

Returns:

random element from the list between the indices min and max

chooseRandom

public static <T> T chooseRandom(List<T> list)

Choose a random item from the given list.

Type Parameters:

T - list element and return type

Parameters:

list - list to choose from

Returns:

random element from the list

consecMap

public static <T,R> List<R> consecMap(List<T> list,
                                            BiFunction<T,T,R> mapping)

Map a list of consecutive items in pairs of two to a new list.

Type Parameters:

T - list item type

R - mapping return and list item return type

Parameters:

list - list of consecutive items

mapping - mapping function

Returns:

list of mapped together elements

consec

public static <T> void consec(List<T> list,
                              BiConsumer<T,T> consumer)

Look at a list of consecutive items in pairs of two.

Type Parameters:

T - list item type

Parameters:

list - list of consecutive items

consumer - consumer working with two consecutive items

consecSum

public static <T> double consecSum(List<T> list,
                                   BiFunction<T,T,Double> mapper)

Consecutively compute a sum over each pair of the list.

Type Parameters:

T - type of list items

Parameters:

list - list to pair together

mapper - mapping to fuse two items into a double

Returns:

sum of the mapped doubles

from

public static <T> List<T> from(Iterator<T> iterator)

Generate a list from an iterator.

Type Parameters:

T - element type

Parameters:

iterator - iterator supplying elements

Returns:

list of elements supplied by the iterator

transpose

public static <T> List<List<T>> transpose(List<List<T>> matrix)

Transpose a two dimensional list matrix.

Type Parameters:

T - element type of the list

Parameters:

matrix - two dimensional list

Returns:

transposed, two dimensional list matrix

printConsecutive

public static <T> String printConsecutive(List<T> list,
                                          Function<T,String> mapper,
                                          String separator)

Prints list of objects in a consecutive order.

Type Parameters:

T - list item type

Parameters:

list - list of objects to be printed

mapper - mapping function to map the objects to strings

separator - item string separator

Returns:

string of printed list

variance

public static double variance(List<? extends Number> list)

Calculates the variance for a list of numbers.

Parameters:

list - list of numbers

Returns:

variance of the values

removeRepeating

public static <T> List<T> removeRepeating(List<T> list)

Remove repeating elements from a list.

Type Parameters:

T - type of list items

Parameters:

list - list with repeating elements

Returns:

list without items repeating

deepClone

public static <T> List<T> deepClone(List<T> items,
                                    UnaryOperator<T> cloner)

Deep clone a list of items.

Type Parameters:

T - type of items

Parameters:

items - items to clone

cloner - cloning method

Returns:

list of deeply cloned items

sum

public static double sum(List<? extends Number> numbers)

Calculate the sum of the list of doubles.

Parameters:

numbers - list of doubles

Returns:

sum of list of doubles

reduce

public static <T> T reduce(List<T> list,
                           BinaryOperator<T> reducer,
                           T optional)

Reduce a list of items to a single item.

Type Parameters:

T - type of list items and return value

Parameters:

list - list of items to reduce

reducer - binary reducing operation

optional - starting value of reduction, gets returned if list is empty

Returns:

result of list reduction

mean

public static double mean(List<Double> numbers)

Computes the mean value of the list of doubles.

Parameters:

numbers - list of doubles

Returns:

mean of list of doubles

map

public static <T,R> List<R> map(List<T> list,
                                      Function<T,R> mapper)

List mapping. Elements mapped to null are ignored.

Type Parameters:

T - input element type

R - output element type

Parameters:

list - list to map

mapper - mapping function

Returns:

list of mapped elements

getMinMaxRatio

public static float getMinMaxRatio(float[] distances)

Compute the ratio of the maximum value divided by the minimum value of the float array.

Parameters:

distances - list of float values

Returns:

max value divided by min value