java.util
Interface Collection

All Superinterfaces:

Iterable

All Known Subinterfaces:

List, Set

All Known Implementing Classes:

AbstractCollection, AbstractList, AbstractSet, ArrayList, HashSet, Vector

public interface Collection

extends Iterable

Collection is the root of the collection hierarchy.

Method Summary

boolean	add(java.lang.Object object) Attempts to add object to the contents of this Collection.
boolean	addAll(Collection collection) Attempts to add all of the objects contained in collection to the contents of this collection.
void	clear() Removes all elements from this Collection, leaving it empty.
boolean	contains(java.lang.Object object) Searches this Collection for the specified object.
boolean	containsAll(Collection collection) Searches this Collection for all objects in the specified Collection.
boolean	equals(java.lang.Object object) Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
int	hashCode() Answers an integer hash code for the receiver.
boolean	isEmpty() Answers if this Collection has no elements, a size of zero.
Iterator	iterator() Returns an instance of Iterator that may be used to access the objects contained by this collection.
boolean	remove(java.lang.Object object) Removes the first occurrence of the specified object from this Collection.
boolean	removeAll(Collection collection) Removes all occurrences in this Collection of each object in the specified Collection.
boolean	retainAll(Collection collection) Removes all objects from this Collection that are not also found in the contents of collection.
int	size() Returns a count of how many objects are contained by this collection.
java.lang.Object[]	toArray() Answers a new array containing all elements contained in this Collection.
java.lang.Object[]	toArray(java.lang.Object[] array) Answers an array containing all elements contained in this Collection.

Method Detail

add

public boolean add(java.lang.Object object)

Attempts to add object to the contents of this Collection.

Parameters:

object - the object to add

Returns:

true if this Collection is modified, false otherwise

Throws:

UnsupportedOperationException - when adding to this Collection is not supported

ClassCastException - when the class of the object is inappropriate for this Collection

IllegalArgumentException - when the object cannot be added to this Collection

addAll

public boolean addAll(Collection collection)

Attempts to add all of the objects contained in collection to the contents of this collection.

Parameters:

collection - the Collection of objects

Returns:

true if this Collection is modified, false otherwise

Throws:

UnsupportedOperationException - when adding to this Collection is not supported

ClassCastException - when the class of an object is inappropriate for this Collection

IllegalArgumentException - when an object cannot be added to this Collection

clear

public void clear()

Removes all elements from this Collection, leaving it empty.

Throws:

UnsupportedOperationException - when removing from this Collection is not supported

See Also:

isEmpty(), size()

contains

public boolean contains(java.lang.Object object)

Searches this Collection for the specified object.

Parameters:

object - the object to search for

Returns:

true if object is an element of this Collection, false otherwise

containsAll

public boolean containsAll(Collection collection)

Searches this Collection for all objects in the specified Collection.

Parameters:

collection - the Collection of objects

Returns:

true if all objects in the specified Collection are elements of this Collection, false otherwise

equals

public boolean equals(java.lang.Object object)

Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.

Parameters:

object - Object the object to compare with this object.

Returns:

boolean true if the object is the same as this object false if it is different from this object.

See Also:

hashCode()

hashCode

public int hashCode()

Answers an integer hash code for the receiver. Objects which are equal answer the same value for this method.

Returns:

the receiver's hash

See Also:

equals(java.lang.Object)

isEmpty

public boolean isEmpty()

Answers if this Collection has no elements, a size of zero.

Returns:

true if this Collection has no elements, false otherwise

See Also:

size()

iterator

public Iterator iterator()

Returns an instance of Iterator that may be used to access the objects contained by this collection.

Specified by:

iterator in interface Iterable

Returns:

an iterator for accessing the collection contents

remove

public boolean remove(java.lang.Object object)

Removes the first occurrence of the specified object from this Collection.

Parameters:

object - the object to remove

Returns:

true if this Collection is modified, false otherwise

Throws:

UnsupportedOperationException - when removing from this Collection is not supported

removeAll

public boolean removeAll(Collection collection)

Removes all occurrences in this Collection of each object in the specified Collection.

Parameters:

collection - the Collection of objects to remove

Returns:

true if this Collection is modified, false otherwise

Throws:

UnsupportedOperationException - when removing from this Collection is not supported

retainAll

public boolean retainAll(Collection collection)

Removes all objects from this Collection that are not also found in the contents of collection.

Parameters:

collection - the Collection of objects to retain

Returns:

true if this Collection is modified, false otherwise

Throws:

UnsupportedOperationException - when removing from this Collection is not supported

size

public int size()

Returns a count of how many objects are contained by this collection.

Returns:

how many objects are contained by this collection

toArray

public java.lang.Object[] toArray()

Answers a new array containing all elements contained in this Collection.

Returns:

an array of the elements from this Collection

toArray

public java.lang.Object[] toArray(java.lang.Object[] array)

Answers an array containing all elements contained in this Collection. If the specified array is large enough to hold the elements, the specified array is used, otherwise an array of the same type is created. If the specified array is used and is larger than this Collection, the array element following the collection elements is set to null.

Parameters:

array - the array

Returns:

an array of the elements from this Collection

Throws:

ArrayStoreException - when the type of an element in this Collection cannot be stored in the type of the specified array