Apache Commons Collections 4.5.0 API
Commons-Collections contains implementations, enhancements and utilities that complement the Java Collections Framework.
The Apache Commons Collections Framework component adds a significant amount of enhancements to the standard JDK collections. These enhancements come in the form of new interfaces, new implementations and utility classes.
     See also the java.util package for the standard Java collections.
  
Main features
Commons-Collections defines a number of key interfaces:
| Interface | Description | 
|---|---|
| Bag | A new Collectionsubinterface that stores each object together
      with the number of occurrences. Methods are provided to get the number of
      occurrences, and to add and remove a certain number of that object. | 
| BidiMap | A new Mapsubinterface that allows lookup from key to value and
      from value to key with equal ease. | 
| OrderedMap | A new Mapsubinterface that is used when a map has an order, but is
      not sorted. Methods enable bidirectional iteration through the map. | 
| MapIterator | A new Iteratorsubinterface specially designed for maps. This iterator
      avoids the need for entrySet iteration of a map, and is simpler to use. | 
| ResettableIterator | A new Iteratorsubinterface that allows the iteration to be reset back
      to the start. Many iterators in this library have this functionality. | 
| A group of functor interfaces that provide plugin behavior to various collections and utilities. | 
In addition to the interfaces, there are many implementations. Consult each subpackage for full details of these.
Packages
Package
Description
Interfaces and utilities shared across all packages.
Implements Bloom filter classes and interfaces.
Implementations of the
 
Collection interface.Implements the
 
Comparator interface.Implements the
 
Iterator interface.Implements collection and map related key/value classes.
Implements the 
List interface.Implements the 
MultiValuedMap interfaces.Implements the
 
MultiSet interface.Extends and customizes the behavior of
 
Properties.Implements the 
Queue interface.Compares two sequences of objects.
Implements the "split map" concept.
Implements the
 
Trie interface.Implements 
KeyAnalyzer.