java.util.Collection<E> |
Known Indirect Subclasses
AbstractCollection
<E>,
AbstractList
<E>,
AbstractQueue
<E>,
AbstractSequentialList
<E>,
AbstractSet
<E>,
ArrayBlockingQueue
<E>,
ArrayDeque
<E>,
ArrayList
<E>,
BlockingDeque
<E>,
BlockingQueue
<E>,
ConcurrentLinkedQueue
<E>,
ConcurrentSkipListSet
<E>,
and
18 others.
|
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.
Public Methods | |||||||||||
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Attempts to add
object
to the contents of this
Collection
(optional).
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|
Attempts to add all of the objects contained in
Collection
to the contents of this
Collection
(optional).
|
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Removes all elements from this
Collection
, leaving it empty (optional).
|
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|
Tests whether this
Collection
contains the specified object.
|
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|
Tests whether this
Collection
contains all objects contained in the
specified
Collection
.
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|
Compares the argument to the receiver, and returns true if they represent
the
same
object using a class specific comparison.
|
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|
Returns an integer hash code for the receiver.
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|
Returns if this
Collection
contains no elements.
|
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|
Returns an instance of
Iterator
that may be used to access the
objects contained by this
Collection
.
|
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|
Removes one instance of the specified object from this
Collection
if one
is contained (optional).
|
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|
Removes all occurrences in this
Collection
of each object in the
specified
Collection
(optional).
|
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|
Removes all objects from this
Collection
that are not also found in the
Collection
passed (optional).
|
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|
Returns a count of how many objects this
Collection
contains.
|
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|
Returns an array containing all elements contained in this
Collection
.
|
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|
Returns a new array containing all elements contained in this
Collection
.
|
[Expand]
Inherited Methods
|
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---|---|---|---|---|---|---|---|---|---|---|---|
From interface
java.lang.Iterable
|
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.
object | the object to add. |
---|
true
if this
Collection
is
modified,
false
otherwise.
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
.
|
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.
collection |
the
Collection
of objects.
|
---|
true
if this
Collection
is modified,
false
otherwise.
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.
|
Removes all elements from this
Collection
, leaving it empty (optional).
UnsupportedOperationException |
if removing from this
Collection
is not supported.
|
---|
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))
.
object | the object to search for. |
---|
true
if object is an element of this
Collection
,
false
otherwise.
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.
|
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
.
collection | the collection of objects. |
---|
true
if all objects in the specified
Collection
are
elements of this
Collection
,
false
otherwise.
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
.
|
Compares the argument to the receiver, and returns true if they represent the same object using a class specific comparison.
object | the object to compare with this object. |
---|
true
if the object is the same as this object and
false
if it is different from this object.
Returns an integer hash code for the receiver. Objects which are equal return the same value for this method.
Returns if this
Collection
contains no elements.
true
if this
Collection
has no elements,
false
otherwise.
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.
Collection
contents.
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)
.
object | the object to remove. |
---|
true
if this
Collection
is modified,
false
otherwise.
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.
|
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.
collection | the collection of objects to remove. |
---|
true
if this
Collection
is modified,
false
otherwise.
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
.
|
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.
collection | the collection of objects to retain. |
---|
true
if this
Collection
is modified,
false
otherwise.
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
.
|
Returns a count of how many objects this
Collection
contains.
Collection
contains, or Integer.MAX_VALUE
if there are more than Integer.MAX_VALUE elements in this
Collection
.
Returns 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.
If the implementation has ordered elements it will return the element
array in the same order as an iterator would return them.
toArray(new Object[0])
behaves exactly the same way as
toArray()
does.
array | the array. |
---|
Collection
.
ArrayStoreException |
if the type of an element in this
Collection
cannot be
stored in the type of the specified array.
|
---|
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.
Collection
.