Inheritance diagram for java.util.Collection< E >:

Public Member Functions
boolean	add (E object)

boolean	addAll (Collection<? extends E > collection)

void	clear ()

boolean	contains (Object object)

boolean	containsAll (Collection<?> collection)

boolean	equals (Object object)

int	hashCode ()

boolean	isEmpty ()

Iterator< E >	iterator ()

boolean	remove (Object object)

boolean	removeAll (Collection<?> collection)

boolean	retainAll (Collection<?> collection)

int	size ()

Object []	toArray ()

Detailed Description

Collection

is the root of the collection hierarchy. It defines operations on data collections and the behavior that they will have in all implementations of

Collection

s.

All direct or indirect implementations of

Collection

should implement at least two constructors. One with no parameters which creates an empty collection and one with a parameter of type

Collection

. This second constructor can be used to create a collection of different type as the initial collection but with the same elements. Implementations of

Collection

cannot be forced to implement these two constructors but at least all implementations under

java.util

do.

Methods that change the content of a collection throw an

UnsupportedOperationException

if the underlying collection does not support that operation, though it's not mandatory to throw such an

Exception

in cases where the requested operation would not change the collection. In these cases it's up to the implementation whether it throws an

UnsupportedOperationException

or not.

Methods marked with (optional) can throw an

UnsupportedOperationException

if the underlying collection doesn't support that method.

Member Function Documentation

◆ add()

boolean java.util.Collection< E >.add ( E object )

Attempts to add

object

to the contents of this

Collection

(optional).

After this method finishes successfully it is guaranteed that the object is contained in the collection.

If the collection was modified it returns

true

,

false

if no changes were made.

An implementation of

Collection

may narrow the set of accepted objects, but it has to specify this in the documentation. If the object to be added does not meet this restriction, then an

IllegalArgumentException

is thrown.

If a collection does not yet contain an object that is to be added and adding the object fails, this method must throw an appropriate unchecked Exception. Returning false is not permitted in this case because it would violate the postcondition that the element will be part of the collection after this method finishes.

Parameters

object the object to add.

Returns: true
if this
Collection
is modified,
false
otherwise.

Exceptions

UnsupportedOperationException	if adding to this Collection is not supported.
ClassCastException	if the class of the object is inappropriate for this collection.
IllegalArgumentException	if the object cannot be added to this Collection .
NullPointerException	if null elements cannot be added to the Collection .

Implemented in java.util.AbstractList< E >, java.util.Vector< E >, java.util.Queue< E >, java.util.ArrayList< E >, java.util.HashSet< E >, java.util.List< E >, java.util.AbstractQueue< E >, java.util.Set< E >, and java.util.AbstractCollection< E >.

◆ addAll()

boolean java.util.Collection< E >.addAll ( Collection<? extends E > collection )

Attempts to add all of the objects contained in

Collection

to the contents of this

Collection

(optional). If the passed

Collection

is changed during the process of adding elements to this

Collection

, the behavior is not defined.

Parameters

collection

the

Collection

of objects.

Returns: true
if this
Collection
is modified,
false
otherwise.

Exceptions

UnsupportedOperationException	if adding to this Collection is not supported.
ClassCastException	if the class of an object is inappropriate for this Collection .
IllegalArgumentException	if an object cannot be added to this Collection .
NullPointerException	if collection is null , or if it contains null elements and this Collection does not support such elements.

Implemented in java.util.Vector< E >, java.util.ArrayList< E >, java.util.AbstractQueue< E >, java.util.List< E >, java.util.AbstractCollection< E >, and java.util.Set< E >.

◆ clear()

void java.util.Collection< E >.clear ( )

Removes all elements from this

Collection

, leaving it empty (optional).

Exceptions

UnsupportedOperationException

if removing from this

Collection

is not supported.

See also: isEmpty; size

Implemented in java.util.AbstractList< E >, java.util.ArrayList< E >, java.util.Vector< E >, java.util.List< E >, java.util.AbstractQueue< E >, java.util.AbstractCollection< E >, java.util.HashSet< E >, and java.util.Set< E >.

◆ contains()

boolean java.util.Collection< E >.contains ( Object object )

Tests whether this

Collection

contains the specified object. Returns

true

if and only if at least one element

elem

in this

Collection

meets following requirement:

(object==null ? elem==null : object.equals(elem))

.

Parameters

object the object to search for.

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

Exceptions

ClassCastException	if the object to look for isn't of the correct type.
NullPointerException	if the object to look for is null and this Collection doesn't support null elements.

Implemented in java.util.ArrayList< E >, java.util.Vector< E >, java.util.List< E >, java.util.AbstractCollection< E >, java.util.HashSet< E >, and java.util.Set< E >.

◆ containsAll()

boolean java.util.Collection< E >.containsAll ( Collection<?> collection )

Tests whether this

Collection

contains all objects contained in the specified

Collection

. If an element

elem

is contained several times in the specified

Collection

, the method returns

true

even if

elem

is contained only once in this

Collection

.

Parameters

collection the collection of objects.

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

Exceptions

ClassCastException	if one or more elements of collection isn't of the correct type.
NullPointerException	if collection contains at least one null element and this Collection doesn't support null elements.
NullPointerException	if collection is null .

Implemented in java.util.Vector< E >, java.util.AbstractCollection< E >, java.util.List< E >, and java.util.Set< E >.

◆ equals()

boolean java.util.Collection< E >.equals ( Object object )

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

Parameters

object the object to compare with this object.

Returns: true
if the object is the same as this object and
false
if it is different from this object.

See also: hashCode

Implemented in java.util.ArrayList< E >, java.util.AbstractList< E >, java.util.Vector< E >, java.util.List< E >, java.util.Set< E >, and java.util.AbstractSet< E >.

◆ hashCode()

int java.util.Collection< E >.hashCode ( )

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

Returns: the receiver's hash.

See also: equals

Implemented in java.util.ArrayList< E >, java.util.AbstractList< E >, java.util.Vector< E >, java.util.List< E >, java.util.Set< E >, and java.util.AbstractSet< E >.

◆ isEmpty()

boolean java.util.Collection< E >.isEmpty ( )

Returns if this

Collection

contains no elements.

Returns: true
if this
Collection
has no elements,
false
otherwise.

See also: size

Implemented in java.util.Vector< E >, java.util.ArrayList< E >, java.util.List< E >, java.util.AbstractCollection< E >, java.util.HashSet< E >, and java.util.Set< E >.

◆ iterator()

Iterator<E> java.util.Collection< E >.iterator ( )

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

Collection

. The order in which the elements are returned by the iterator is not defined. Only if the instance of the

Collection

has a defined order the elements are returned in that order.

Returns: an iterator for accessing the
Collection
contents.

Implemented in java.util.AbstractList< E >, java.util.ArrayList< E >, java.util.List< E >, java.util.AbstractCollection< E >, java.util.HashSet< E >, and java.util.Set< E >.

◆ remove()

boolean java.util.Collection< E >.remove ( Object object )

Removes one instance of the specified object from this

Collection

if one is contained (optional). The element

elem

that is removed complies with

(object==null ? elem==null : object.equals(elem)

.

Parameters

object the object to remove.

Returns: true
if this
Collection
is modified,
false
otherwise.

Exceptions

UnsupportedOperationException	if removing from this Collection is not supported.
ClassCastException	if the object passed is not of the correct type.
NullPointerException	if object is null and this Collection doesn't support null elements.

Implemented in java.util.Vector< E >, java.util.ArrayList< E >, java.util.List< E >, java.util.AbstractCollection< E >, java.util.HashSet< E >, and java.util.Set< E >.

◆ removeAll()

boolean java.util.Collection< E >.removeAll ( Collection<?> collection )

Removes all occurrences in this

Collection

of each object in the specified

Collection

(optional). After this method returns none of the elements in the passed

Collection

can be found in this

Collection

anymore.

Parameters

collection the collection of objects to remove.

Returns: true
if this
Collection
is modified,
false
otherwise.

Exceptions

UnsupportedOperationException	if removing from this Collection is not supported.
ClassCastException	if one or more elements of collection isn't of the correct type.
NullPointerException	if collection contains at least one null element and this Collection doesn't support null elements.
NullPointerException	if collection is null .

Implemented in java.util.Vector< E >, java.util.AbstractCollection< E >, java.util.List< E >, java.util.Set< E >, and java.util.AbstractSet< E >.

◆ retainAll()

boolean java.util.Collection< E >.retainAll ( Collection<?> collection )

Removes all objects from this

Collection

that are not also found in the

Collection

passed (optional). After this method returns this

Collection

will only contain elements that also can be found in the

Collection

passed to this method.

Parameters

collection the collection of objects to retain.

Returns: true
if this
Collection
is modified,
false
otherwise.

Exceptions

UnsupportedOperationException	if removing from this Collection is not supported.
ClassCastException	if one or more elements of collection isn't of the correct type.
NullPointerException	if collection contains at least one null element and this Collection doesn't support null elements.
NullPointerException	if collection is null .

Implemented in java.util.Vector< E >, java.util.AbstractCollection< E >, java.util.List< E >, and java.util.Set< E >.

◆ size()

int java.util.Collection< E >.size ( )

Returns a count of how many objects this

Collection

contains.

Returns: how many objects this
Collection
contains, or Integer.MAX_VALUE if there are more than Integer.MAX_VALUE elements in this
Collection
.

Implemented in java.util.Vector< E >, java.util.AbstractCollection< E >, java.util.ArrayList< E >, java.util.List< E >, java.util.Set< E >, and java.util.HashSet< E >.

◆ toArray()

Object [] java.util.Collection< E >.toArray ( )

Returns a new array containing all elements contained in this

Collection

.

If the implementation has ordered elements it will return the element array in the same order as an iterator would return them.

The array returned does not reflect any changes of the

Collection

. A new array is created even if the underlying data structure is already an array.

Returns: an array of the elements from this
Collection
.

Implemented in java.util.Vector< E >, java.util.ArrayList< E >, java.util.AbstractCollection< E >, java.util.List< E >, and java.util.Set< E >.

The documentation for this interface was generated from the following file:

src/java/util/Collection.java

Public Member Functions

Detailed Description

Member Function Documentation

◆ add()

◆ addAll()

◆ clear()

◆ contains()

◆ containsAll()

◆ equals()

◆ hashCode()

◆ isEmpty()

◆ iterator()

◆ remove()

◆ removeAll()

◆ retainAll()

◆ size()

◆ toArray()