com.github.bicoco

Class Helpers

java.lang.Object

com.github.bicoco.Helpers

public class Helpers
extends Object

This library is a collection of auxiliary methods for accessing, searching and otherwise manipulating List objects. This class is a wrapper for the methods of api.

Since:

1.3

Constructor Summary

Constructors

Constructor and Description
Helpers()

Method Summary

Modifier and Type	Method and Description
static <T> boolean	all(List<T> list, ConditionFunction<T> function) Returns true if all of the values in the list pass the predicate truth test
static <T> boolean	any(List<T> list, ConditionFunction<T> function) Returns true if any of the values in the list pass the predicate truth test
static <T> T	at(List<T> list, int index) Return the element at index.
static <T> void	compact$(List<T> list) Remove null values in list
static <T> int	count(List<T> list) Return size of list or 0 to empty list.
static <T> int	count(List<T> list, ConditionFunction<T> function) Return size of list where function returns true, or 0 to empty list.
static <T> List<T>	drop(List<T> list, int n) Get the elements of list excluding the first n elements
static <T> void	each(List<T> list, EachFunction<T> function) Execute a custom action for each element of list.
static <T> T	fetch(List<T> list, int index) Identical to List.get(int)
static <T> T	fetch(List<T> list, int index, T def) Null-safe, get element at index, with default value.
static <T> T	first(List<T> list) Get the first element of list.
static <T> boolean	isEmpty(List<T> list) Check if list is empty
static <T> boolean	isNotEmpty(List<T> list) Check if list is not empty
static <T> T	last(List<T> list) Get the last element of list.
static <T> List<T>	map(List<T> list, MapFunction<T> function) Return a new list of same type element, applying new value for each element.
static <T> void	map$(List<T> list, MapFunction<T> function) Modifing list applying new value for each element.
static <T> void	push(List<T> list, T... ts) Adding multiple elements to the end of list.
static <T> ListHelper<T>	push(List<T> list, T t) Adding element to the end of list.
static <T,R> R	reduce(List<T> list, R initialValue, ReduceFunction<T,R> function) Transform a list on a single value
static <T> List<T>	reject(List<T> list, ConditionFunction<T> function) Select all elements that condition returns false.
static <T> void	reject$(List<T> list, ConditionFunction<T> function) Select all elements that condition returns false.
static <T> List<T>	select(List<T> list, ConditionFunction<T> function) Select all elements that condition returns true.
static <T> void	select$(List<T> list, ConditionFunction<T> function) Select all elements that condition returns true.
static <T> int	size(List<T> list) Identical to List#size()
static <T> List<T>	take(List<T> list, int n) Get the first n elements of list
static <T,R> List<R>	transform(List<T> list, TransformFunction<T,R> function) Return a new list of another type element, applying a function for each element.

Methods inherited from class java.lang.Object

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

Constructor Detail

Helpers

public Helpers()

Method Detail

each

public static <T> void each(List<T> list,
                            EachFunction<T> function)

Execute a custom action for each element of list.

Parameters:

list - list of elements to iterate

function - function to execute in each element

map

public static <T> List<T> map(List<T> list,
                              MapFunction<T> function)

Return a new list of same type element, applying new value for each element.

Parameters:

list - list of elements to iterate

function - function to apply in each value that returns the new value

Returns:

changed list of same type element

transform

public static <T,R> List<R> transform(List<T> list,
                                      TransformFunction<T,R> function)

Return a new list of another type element, applying a function for each element.

Parameters:

list - list of elements to iterate

function - function to apply in each element of list

Returns:

list of elements transformed

select

public static <T> List<T> select(List<T> list,
                                 ConditionFunction<T> function)

Select all elements that condition returns true.

Parameters:

list - list of elements to iterate

function - Apply in each element and select if returns true.

Returns:

list of elements that the condition is true.

reject

public static <T> List<T> reject(List<T> list,
                                 ConditionFunction<T> function)

Select all elements that condition returns false.

Parameters:

list - list of elements to iterate

function - Apply in each element and select if returns true.

Returns:

list of elements that the condition is false.

map$

public static <T> void map$(List<T> list,
                            MapFunction<T> function)

Modifing list applying new value for each element.

Parameters:

list - values list of elements

function - function to apply in each value that returns the new value

select$

public static <T> void select$(List<T> list,
                               ConditionFunction<T> function)

Select all elements that condition returns true.

Parameters:

list - values list of elements

function - Apply in each element and select if returns true.

reject$

public static <T> void reject$(List<T> list,
                               ConditionFunction<T> function)

Select all elements that condition returns false.

Parameters:

list - values list of elements

function - Apply in each element and select if returns false.

compact$

public static <T> void compact$(List<T> list)

Remove null values in list

Parameters:

list - values list of elements

push

public static <T> void push(List<T> list,
                            T... ts)

Adding multiple elements to the end of list.

Parameters:

list - values list of elements

ts - elements to push

push

public static <T> ListHelper<T> push(List<T> list,
                                     T t)

Adding element to the end of list.

Parameters:

list - values list of elements

t - element to push

Returns:

ListHelper to chaining methods

at

public static <T> T at(List<T> list,
                       int index)

Return the element at index. Returns null if index is out of range. Negative index counts from the end of list.

Parameters:

index - index of element

Returns:

Element at the index

fetch

public static <T> T fetch(List<T> list,
                          int index)

Identical to List.get(int)

Parameters:

list - list of elements

index - index of element

Returns:

The element at index

Throws:

IndexOutOfBoundsException

fetch

public static <T> T fetch(List<T> list,
                          int index,
                          T def)

Null-safe, get element at index, with default value.

Parameters:

list - list of elements

index - index of element

def - Default value

Returns:

element of list or default value

first

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

Get the first element of list.

Parameters:

list - list of elements

Returns:

the first element

last

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

Get the last element of list.

Parameters:

list - list of elements

Returns:

the last element

take

public static <T> List<T> take(List<T> list,
                               int n)

Get the first n elements of list

Parameters:

list - values list of type T

n - number of elements

Returns:

List of the first n elements

drop

public static <T> List<T> drop(List<T> list,
                               int n)

Get the elements of list excluding the first n elements

Parameters:

list - list of elements

n - number of elements to exclude

Returns:

list of the elements

isEmpty

public static <T> boolean isEmpty(List<T> list)

Check if list is empty

Returns:

true if list is null or size is 0.

isNotEmpty

public static <T> boolean isNotEmpty(List<T> list)

Check if list is not empty

Returns:

true if list is not null and size is greater than 0.

size

public static <T> int size(List<T> list)

Identical to List#size()

Parameters:

list - the list of elements

Returns:

the size of list

count

public static <T> int count(List<T> list)

Return size of list or 0 to empty list.

Returns:

the size of list

count

public static <T> int count(List<T> list,
                            ConditionFunction<T> function)

Return size of list where function returns true, or 0 to empty list.

Parameters:

list - the list of elements

function - the condition to consider element in count

Returns:

the size of list

all

public static <T> boolean all(List<T> list,
                              ConditionFunction<T> function)

Returns true if all of the values in the list pass the predicate truth test

Parameters:

function - apply in each element and return false if one of them fail

Returns:

true if all elements pass on test

any

public static <T> boolean any(List<T> list,
                              ConditionFunction<T> function)

Returns true if any of the values in the list pass the predicate truth test

Parameters:

function - apply in each element and return true if one of them pass

Returns:

true if any elements pass on test

reduce

public static <T,R> R reduce(List<T> list,
                             R initialValue,
                             ReduceFunction<T,R> function)

Transform a list on a single value

Parameters:

list - list of elements

initialValue - initial value of the to be returned

function - the reduce function

Returns:

the value

Since:

1.2