Commons-Collections contains implementations, enhancements and utilities that complement the Java Collections Framework.
The Apache Jakarta 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 Collection subinterface that stores each object together
with the number of occurances. Methods are provided to get the number of
occurances, and to add and remove a certain number of that object.
|
Buffer
|
A new Collection subinterface that allows objects to be removed
in some well-defined order. Methods enable the next item to be peeked and removed.
|
BidiMap
|
A new Map subinterface that allows lookup from key to value and
from value to key with equal ease.
|
OrderedMap
|
A new Map subinterface that is used when a map has an order, but is
not sorted. Methods enable bidriectional iteration through the map.
|
MapIterator
|
A new Iterator subinterface specially designed for maps. This iterator
avoids the need for entrySet iteration of a map, and is simpler to use.
|
ResettableIterator
|
A new Iterator subinterface that allows the iteration to be reset back
to the start. Many iterators in this library have this functionality.
|
ClosurePredicateTransformerFactory |
A group of functor interfaces that provide plugin behaviour to various collections and utilities. |
In addition to the interfaces, there are many implementations. Consult each subpackage for full details of these.
| Package | Description |
|---|---|
| org.apache.commons.collections |
This package contains the interfaces and utilities shared across all the subpackages of this component.
|
| org.apache.commons.collections.bag | |
| org.apache.commons.collections.bidimap | |
| org.apache.commons.collections.buffer |
This package contains implementations of the
Buffer interface. |
| org.apache.commons.collections.collection |
This package contains implementations of the
Collection interface. |
| org.apache.commons.collections.comparators |
This package contains implementations of the
Comparator interface. |
| org.apache.commons.collections.functors |
This package contains implementations of the
Closure,
Predicate,
Transformer and
Factory interfaces. |
| org.apache.commons.collections.iterators |
This package contains implementations of the
Iterator interface. |
| org.apache.commons.collections.keyvalue |
This package contains implementations of collection and map related key/value classes.
|
| org.apache.commons.collections.list |
This package contains implementations of the
List interface. |
| org.apache.commons.collections.map | |
| org.apache.commons.collections.set |