AbstractCollection
abstract class AbstractCollection<E : Any!> : MutableCollection<E>
kotlin.Any | |
↳ | java.util.AbstractCollection |
This class provides a skeletal implementation of the Collection
interface, to minimize the effort required to implement this interface.
To implement an unmodifiable collection, the programmer needs only to extend this class and provide implementations for the iterator
and size
methods. (The iterator returned by the iterator
method must implement hasNext
and next
.)
To implement a modifiable collection, the programmer must additionally override this class's add
method (which otherwise throws an UnsupportedOperationException
), and the iterator returned by the iterator
method must additionally implement its remove
method.
The programmer should generally provide a void (no argument) and Collection
constructor, as per the recommendation in the Collection
interface specification.
The documentation for each non-abstract method in this class describes its implementation in detail. Each of these methods may be overridden if the collection being implemented admits a more efficient implementation.
This class is a member of the Java Collections Framework.
Summary
Protected constructors | |
---|---|
Sole constructor. |
Public methods | |
---|---|
open Boolean |
add(element: E) Ensures that this collection contains the specified element (optional operation). |
open Boolean |
addAll(elements: Collection<E>) Adds all of the elements in the specified collection to this collection (optional operation). |
open Unit |
clear() Removes all of the elements from this collection (optional operation). |
open Boolean |
contains(element: E?) Returns |
open Boolean |
containsAll(elements: Collection<E>) Returns |
open Boolean |
isEmpty() Returns |
abstract MutableIterator<E> |
iterator() Returns an iterator over the elements contained in this collection. |
open Boolean |
remove(element: E?) Removes a single instance of the specified element from this collection, if it is present (optional operation). |
open Boolean |
removeAll(elements: Collection<E>) Removes all of this collection's elements that are also contained in the specified collection (optional operation). |
open Boolean |
retainAll(elements: Collection<E>) Retains only the elements in this collection that are contained in the specified collection (optional operation). |
open Array<Any!> |
toArray() Returns an array containing all of the elements in this collection. |
open Array<T> |
Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. |
open String |
toString() Returns a string representation of this collection. |
Properties | |
---|---|
abstract Int |
Protected constructors
AbstractCollection
protected AbstractCollection()
Sole constructor. (For invocation by subclass constructors, typically implicit.)
Public methods
add
open fun add(element: E): Boolean
Ensures that this collection contains the specified element (optional operation). Returns true
if this collection changed as a result of the call. (Returns false
if this collection does not permit duplicates and already contains the specified element.)
Collections that support this operation may place limitations on what elements may be added to this collection. In particular, some collections will refuse to add null
elements, and others will impose restrictions on the type of elements that may be added. Collection classes should clearly specify in their documentation any restrictions on what elements may be added.
If a collection refuses to add a particular element for any reason other than that it already contains the element, it must throw an exception (rather than returning false
). This preserves the invariant that a collection always contains the specified element after this call returns.
Parameters | |
---|---|
e |
element whose presence in this collection is to be ensured |
Return | |
---|---|
Boolean |
true if this collection changed as a result of the call |
Exceptions | |
---|---|
java.lang.UnsupportedOperationException |
if the add operation is not supported by this collection |
java.lang.ClassCastException |
if the class of the specified element prevents it from being added to this collection |
java.lang.NullPointerException |
if the specified element is null and this collection does not permit null elements |
java.lang.IllegalArgumentException |
if some property of the element prevents it from being added to this collection |
java.lang.IllegalStateException |
if the element cannot be added at this time due to insertion restrictions |
addAll
open fun addAll(elements: Collection<E>): Boolean
Adds all of the elements in the specified collection to this collection (optional operation). The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. (This implies that the behavior of this call is undefined if the specified collection is this collection, and this collection is nonempty.)
Parameters | |
---|---|
c |
collection containing elements to be added to this collection |
Return | |
---|---|
Boolean |
true if this collection changed as a result of the call |
Exceptions | |
---|---|
java.lang.UnsupportedOperationException |
if the addAll operation is not supported by this collection |
java.lang.ClassCastException |
if the class of an element of the specified collection prevents it from being added to this collection |
java.lang.NullPointerException |
if the specified collection contains a null element and this collection does not permit null elements, or if the specified collection is null |
java.lang.IllegalArgumentException |
if some property of an element of the specified collection prevents it from being added to this collection |
java.lang.IllegalStateException |
if not all the elements can be added at this time due to insertion restrictions |
See Also
clear
open fun clear(): Unit
Removes all of the elements from this collection (optional operation). The collection will be empty after this method returns.
Exceptions | |
---|---|
java.lang.UnsupportedOperationException |
if the clear operation is not supported by this collection |
contains
open fun contains(element: E?): Boolean
Returns true
if this collection contains the specified element. More formally, returns true
if and only if this collection contains at least one element e
such that Objects.equals(o, e)
.
Parameters | |
---|---|
o |
element whose presence in this collection is to be tested |
Return | |
---|---|
Boolean |
true if this collection contains the specified element |
Exceptions | |
---|---|
java.lang.ClassCastException |
if the type of the specified element is incompatible with this collection (optional) |
java.lang.NullPointerException |
if the specified element is null and this collection does not permit null elements (optional) |
containsAll
open fun containsAll(elements: Collection<E>): Boolean
Returns true
if this collection contains all of the elements in the specified collection.
Parameters | |
---|---|
c |
collection to be checked for containment in this collection |
Return | |
---|---|
Boolean |
true if this collection contains all of the elements in the specified collection |
Exceptions | |
---|---|
java.lang.ClassCastException |
if the types of one or more elements in the specified collection are incompatible with this collection (optional) |
java.lang.NullPointerException |
if the specified collection contains one or more null elements and this collection does not permit null elements (optional), or if the specified collection is null. |
See Also
isEmpty
open fun isEmpty(): Boolean
Returns true
if this collection contains no elements.
Return | |
---|---|
Boolean |
true if this collection contains no elements |
iterator
abstract fun iterator(): MutableIterator<E>
Returns an iterator over the elements contained in this collection.
Return | |
---|---|
MutableIterator<E> |
an iterator over the elements contained in this collection |
remove
open fun remove(element: E?): Boolean
Removes a single instance of the specified element from this collection, if it is present (optional operation). More formally, removes an element e
such that Objects.equals(o, e)
, if this collection contains one or more such elements. Returns true
if this collection contained the specified element (or equivalently, if this collection changed as a result of the call).
Parameters | |
---|---|
o |
element to be removed from this collection, if present |
Return | |
---|---|
Boolean |
true if an element was removed as a result of this call |
Exceptions | |
---|---|
java.lang.ClassCastException |
if the type of the specified element is incompatible with this collection (optional) |
java.lang.NullPointerException |
if the specified element is null and this collection does not permit null elements (optional) |
java.lang.UnsupportedOperationException |
if the remove operation is not supported by this collection |
removeAll
open fun removeAll(elements: Collection<E>): Boolean
Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection.
Parameters | |
---|---|
c |
collection containing elements to be removed from this collection |
Return | |
---|---|
Boolean |
true if this collection changed as a result of the call |
Exceptions | |
---|---|
java.lang.UnsupportedOperationException |
if the removeAll method is not supported by this collection |
java.lang.ClassCastException |
if the types of one or more elements in this collection are incompatible with the specified collection (optional) |
java.lang.NullPointerException |
if this collection contains one or more null elements and the specified collection does not support null elements (optional), or if the specified collection is null |
See Also
retainAll
open fun retainAll(elements: Collection<E>): Boolean
Retains only the elements in this collection that are contained in the specified collection (optional operation). In other words, removes from this collection all of its elements that are not contained in the specified collection.
Parameters | |
---|---|
c |
collection containing elements to be retained in this collection |
Return | |
---|---|
Boolean |
true if this collection changed as a result of the call |
Exceptions | |
---|---|
java.lang.UnsupportedOperationException |
if the retainAll operation is not supported by this collection |
java.lang.ClassCastException |
if the types of one or more elements in this collection are incompatible with the specified collection (optional) |
java.lang.NullPointerException |
if this collection contains one or more null elements and the specified collection does not permit null elements (optional), or if the specified collection is null |
See Also
toArray
open fun toArray(): Array<Any!>
Returns an array containing all of the elements in this collection. If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order. The returned array's runtime component type is Object
.
The returned array will be "safe" in that no references to it are maintained by this collection. (In other words, this method must allocate a new array even if this collection is backed by an array). The caller is thus free to modify the returned array.
Return | |
---|---|
Array<Any!> |
an array, whose type is Object , containing all of the elements in this collection |
toArray
open fun <T : Any!> toArray(a: Array<T>): Array<T>
Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. If the collection fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this collection.
If this collection fits in the specified array with room to spare (i.e., the array has more elements than this collection), the element in the array immediately following the end of the collection is set to null
. (This is useful in determining the length of this collection only if the caller knows that this collection does not contain any null
elements.)
If this collection makes any guarantees as to what order its elements are returned by its iterator, this method must return the elements in the same order.
Parameters | |
---|---|
<T> |
the component type of the array to contain the collection |
a |
Array<T>: the array into which the elements of this collection are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose. |
Return | |
---|---|
Array<T> |
an array containing all of the elements in this collection |
Exceptions | |
---|---|
java.lang.ArrayStoreException |
if the runtime type of any element in this collection is not assignable to the runtime component type of the specified array |
java.lang.NullPointerException |
if the specified array is null |
toString
open fun toString(): String
Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"
). Adjacent elements are separated by the characters ", "
(comma and space). Elements are converted to strings as by String#valueOf(Object)
.
Return | |
---|---|
String |
a string representation of this collection |
Properties
size
abstract val size: Int
Return | |
---|---|
Int |
the number of elements in this collection |