apache-comnons系列之commons-collections4 org.apache.commons.collections4.CollectionUtils学习笔记

apache-comnons系列之commons-collections4 org.apache.commons.collections4.CollectionUtils学习笔记

概述

Collection、List、Set、Map关系图学习笔记1(4/4/3/4)

http://blog.csdn.net/undergrowth/article/details/44066917#comments

http://blog.csdn.net/undergrowth/article/details/46518929

CollectionUtils

ListUtils

SetUtils

QueueUtils

MapUtils

BagUtils

Bag

Defines a collection that counts the number of times an object appears in the collection.

Transformer

Defines a functor interface implemented by classes that transform one object into another.

Predicate

Defines a functor interface implemented by classes that perform a predicate test on an object.

测试

org.apache.commons.collections4.CollectionUtilsTest

getCardinalityMap

Returns a {@link Map} mapping each unique element in the given {@link Collection} to an {@link Integer} representing the number of occurrences of that element in the {@link Collection}.

containsAll

Returns

true

iff all elements of {@code coll2} are also contained in {@code coll1}. The cardinality of values in {@code coll2} is not taken into account,which is the same behavior as {@link Collection#containsAll(Collection)}.

union/intersection/subtract

transform

Transform the collection by applying a Transformer to each element

This routine is best for Lists, for which set() is used to do the transformations “in place.” For other Collections, clear() and addAll() are used to replace elements.

collect

Returns a new Collection containing all elements of the input collection transformed by the given transformer.

select

Selects all elements from input collection which match the given predicate into an output collection.

filter

Filter the collection by applying a Predicate to each element. If the predicate returns false, remove the element.

collate

merges two sorted Collections, a and b, into a single, sorted List such that the natural ordering of the elements is retained.