Collection is a Java interface for common abstract data types that store multiple items in them.
- Lists are indexed sequences with duplication. The two most common types are ArrayLists and Linked Lists.
- Sets are non-indexed sequences with no duplication. (That is, every value in a set is unique.)
- Maps are key-value pairs. See Hashing and Hash Tables for a description on one common map implementation, the HashMap. All keys in a map must be unique, but values can be duplicated.
- Stacks and Queues are two ordered collections that have two core behaviors:
- push(T x): puts x on the top.
- pop(): Removes the first item. (See the stacks and queues page for more information.)
Common Functions #
- Membership tests
containsAll()that can determine whether or not an element is in the collection.
size()to get the number of items in the collection.
isEmpty()returns true if there is nothing in the collection.
iterator()returns an Iterator object to go through all the values in the collection.
toArray()converts the collection to a standard Java array.
- Optional functions that aren’t implemented in the interface:
add, addAll, clear, remove, removeAll, retainAll (intersection)
UnsupportedOperationExceptionif not implemented.