Package it.tidalwave.util

Class CollectionUtils

java.lang.Object

it.tidalwave.util.CollectionUtils

public final class CollectionUtils
extends Object

This class contains a bunch of utility methods for manipulating lists.

Since:

3.2-ALPHA-13

Author:

Fabrizio Giudici

Status: stable API

Constructor Summary

Constructors

Constructor	Description
CollectionUtils()

Method Summary

Modifier and Type	Method	Description
static <T> List<T>	concat(List<? extends T> list, T object)	Appends a list to an object.
static <T> List<T>	concatAll(Collection<? extends T>... collections)	Returns a concatenation of the given Collections.
static <T> T	head(List<? extends T> list)	Returns the first element of a list.
static <T> Optional<T>	optionalHead(List<? extends T> list)	Returns the (optional) first element of a list.
static <T> List<T>	reversed(List<? extends T> list)	Reverses a list.
static <T> List<T>	safeSubList(List<? extends T> list, int from, int to)	Return a sublist of the original List, from the given from and to index (not included).
static <T extends Comparable<? super T>> List<T>	sorted(List<? extends T> list)	Sorts a list.
static <T> List<T>	sorted(List<? extends T> list, Comparator<? super T> comparator)	Sorts a list with a given Comparator.
static <T> List<List<T>>	split(List<? extends T> list, int... boundaries)	Splits a given List at a set of boundaries.
static <T> List<T>	tail(List<? extends T> list)	Returns the tail element of a list, that is a list without the first element.

Methods inherited from class java.lang.Object

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

Constructor Details

CollectionUtils

public CollectionUtils()

Method Details

concat

@Nonnull
public static <T> List<T> concat(@Nonnull
 List<? extends T> list,
 @Nonnull
 T object)

Appends a list to an object. The resulting list is mutable.

Type Parameters:

T - the type of list items

Parameters:

list - the list

object - the list to append

Returns:

the list with the appended object

concatAll

@Nonnull
@SafeVarargs
public static <T> List<T> concatAll(@Nonnull
 Collection<? extends T>... collections)

Returns a concatenation of the given Collections.

Type Parameters:

T - the static type

Parameters:

collections - the input collections

Returns:

the concatenation

reversed

@Nonnull
public static <T> List<T> reversed(@Nonnull
 List<? extends T> list)

Reverses a list. The resulting list is mutable.

Type Parameters:

T - the type of list items

Parameters:

list - the list

Returns:

the reversed list

sorted

@Nonnull
public static <T extends Comparable<? super T>>
List<T> sorted(@Nonnull
 List<? extends T> list)

Sorts a list. The resulting list is mutable.

Type Parameters:

T - the type of list items

Parameters:

list - the list

Returns:

the sorted list

Since:

3.2-ALPHA-13

sorted

@Nonnull
public static <T> List<T> sorted(@Nonnull
 List<? extends T> list,
 @Nonnull
 Comparator<? super T> comparator)

Sorts a list with a given Comparator. The resulting list is mutable.

Type Parameters:

T - the type of list items

Parameters:

list - the list

comparator - the comparator

Returns:

the sorted list

Since:

3.2-ALPHA-13

optionalHead

@Nonnull
public static <T> Optional<T> optionalHead(@Nonnull
 List<? extends T> list)

Returns the (optional) first element of a list.

Type Parameters:

T - the type of list items

Parameters:

list - the list

Returns:

the first element

head

@Nonnull
public static <T> T head(@Nonnull
 List<? extends T> list)

Returns the first element of a list.

Type Parameters:

T - the type of list items

Parameters:

list - the list (cannot be empty)

Returns:

the first element

Throws:

IllegalArgumentException - if the list is empty

tail

@Nonnull
public static <T> List<T> tail(@Nonnull
 List<? extends T> list)

Returns the tail element of a list, that is a list without the first element. The tail of an empty list is an empty list. The resulting list is mutable.

Type Parameters:

T - the type of list items

Parameters:

list - the list

Returns:

the tail of the list

safeSubList

@Nonnull
public static <T> List<T> safeSubList(@Nonnull
 List<? extends T> list,
 int from,
 int to)

Return a sublist of the original List, from the given from and to index (not included). If the from index is negative and/or the to index is lower than the from index or if an attempt is made to read before the start or past the end of the list, truncation silently occurs.

Type Parameters:

T - the static type

Parameters:

list - the original list

from - the first index (included)

to - the last index (excluded)

Returns:

the sublist

Since:

3.2-ALPHA-17

split

@Nonnull
public static <T> List<List<T>> split(@Nonnull
 List<? extends T> list,
 int... boundaries)

Splits a given List at a set of boundaries. Each boundary is the starting point of a sublist to be returned.

Type Parameters:

T - the static type

Parameters:

list - the original list

boundaries - the boundaries

Returns:

a list of sublists

Since:

3.2-ALPHA-17