Section 11.4. General Collections Methods | Java for ColdFusion Developers

11.4 General Collections Methods

JDK 1.2 added to the collections significantly. It can be difficult to keep them straight, because their names ( TreeMap, Map, HashMap, HashTable, HashSet ) are so similar.

The Collection interface defines generic methods that you can use with any of the specific collection types. These are listed in Table 11.1.

Table 11.1. Generic Methods that Work with All Collections

Method	Purpose
`add(Object o)`	Inserts the specified element into the collection. Returns `true` .
`addAll(Collection c)`	Adds all of the elements in the specified collection to this collection. Returns `true` .
`clear()`	Removes all elements from this collection.
`contains(Object o)`	Returns a boolean `true` if the specified element is contained in this collection.
`containsAll(Collection c)`	Returns `true` if all of the elements specified are in this collection.
`equals(Object o)`	Compares the object specified to determine equality.
`hashCode()`	Returns the hashcode for this collection.
`isEmpty()`	Returns `true` if there are no elements in this collection.
`iterator()`	Returns an iterator for iterating through the objects in the collection.
`remove(Object o)`	Returns `true` if the element has been successfully removed from the collection.
`removeAll(Collection c)`	Removes all of the elements in this collection. Returns `true` .
`retainAll(Collection c)`	Retains only the elements specified in the passed collection. All others are removed.
`size ()`	Returns the number of elements in this collection.
`toArray()`	Returns an array containing all of the elements in this collection.

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