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FlexDoc/Javadoc 2.0 Demo Java Doc |
Interface Set<E>
Type Parameters:
E - the type of elements maintained by this set
All Superinterfaces:
All Known Subinterfaces:
All Known Implementing Classes:
public interface Set<E>
A collection that contains no duplicate elements. More formally, sets
contain no pair of elements
e1 and
e2 such that
e1.equals(e2), and at most one null element. As implied by
its name, this interface models the mathematical
set abstraction.
The Set interface places additional stipulations, beyond those
inherited from the Collection interface, on the contracts of all
constructors and on the contracts of the add, equals and
hashCode methods. Declarations for other inherited methods are
also included here for convenience. (The specifications accompanying these
declarations have been tailored to the Set interface, but they do
not contain any additional stipulations.)
The additional stipulation on constructors is, not surprisingly,
that all constructors must create a set that contains no duplicate elements
(as defined above).
Note: Great care must be exercised if mutable objects are used as set
elements. The behavior of a set is not specified if the value of an object
is changed in a manner that affects equals comparisons while the
object is an element in the set. A special case of this prohibition is
that it is not permissible for a set to contain itself as an element.
Some set implementations have restrictions on the elements that
they may contain. For example, some implementations prohibit null elements,
and some have restrictions on the types of their elements. Attempting to
add an ineligible element throws an unchecked exception, typically
NullPointerException or ClassCastException. Attempting
to query the presence of an ineligible element may throw an exception,
or it may simply return false; some implementations will exhibit the former
behavior and some will exhibit the latter. More generally, attempting an
operation on an ineligible element whose completion would not result in
the insertion of an ineligible element into the set may throw an
exception or it may succeed, at the option of the implementation.
Such exceptions are marked as "optional" in the specification for this
interface.
The Set.of and
Set.copyOf static factory methods
provide a convenient way to create unmodifiable sets. The Set
instances created by these methods have the following characteristics:
- They are unmodifiable. Elements cannot
be added or removed. Calling any mutator method on the Set
will always cause UnsupportedOperationException to be thrown.
However, if the contained elements are themselves mutable, this may cause the
Set to behave inconsistently or its contents to appear to change.
- They disallow null elements. Attempts to create them with
null elements result in NullPointerException.
- They are serializable if all elements are serializable.
- They reject duplicate elements at creation time. Duplicate elements
passed to a static factory method result in IllegalArgumentException.
- The iteration order of set elements is unspecified and is subject to change.
- They are value-based.
Programmers should treat instances that are equal
as interchangeable and should not use them for synchronization, or
unpredictable behavior may occur. For example, in a future release,
synchronization may fail. Callers should make no assumptions
about the identity of the returned instances. Factories are free to
create new instances or reuse existing ones.
- They are serialized as specified on the
Serialized Form
page.
This interface is a member of the
Java Collections Framework.
Since:
1.2
Author:
Josh Bloch, Neal Gafter
See Also:
Method Summary |
boolean |
Adds the specified element to this set if it is not already present
(optional operation).
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boolean |
Adds all of the elements in the specified collection to this set if
they're not already present (optional operation).
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void |
Removes all of the elements from this set (optional operation).
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boolean |
Returns true if this set contains the specified element.
|
boolean |
Returns true if this set contains all of the elements of the
specified collection.
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boolean |
Compares the specified object with this set for equality.
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int |
Returns the hash code value for this set.
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boolean |
Returns true if this set contains no elements.
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Returns an iterator over the elements in this set.
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Returns an unmodifiable set containing zero elements.
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Returns an unmodifiable set containing one element.
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Returns an unmodifiable set containing two elements.
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Returns an unmodifiable set containing three elements.
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Returns an unmodifiable set containing four elements.
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Returns an unmodifiable set containing five elements.
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Returns an unmodifiable set containing six elements.
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Returns an unmodifiable set containing seven elements.
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of( E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8)
Returns an unmodifiable set containing eight elements.
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of( E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9)
Returns an unmodifiable set containing nine elements.
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of( E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10)
Returns an unmodifiable set containing ten elements.
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Returns an unmodifiable set containing an arbitrary number of elements.
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boolean |
Removes the specified element from this set if it is present
(optional operation).
|
boolean |
Removes from this set all of its elements that are contained in the
specified collection (optional operation).
|
boolean |
Retains only the elements in this set that are contained in the
specified collection (optional operation).
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int |
Returns the number of elements in this set (its cardinality).
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Creates a Spliterator over the elements in this set.
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Returns an array containing all of the elements in this set.
|
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Returns an array containing all of the elements in this set; the
runtime type of the returned array is that of the specified array.
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Methods inherited from interface java.util. Collection |
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Methods inherited from interface java.lang. Iterable |
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Returns the number of elements in this set (its cardinality). If this
set contains more than
Integer.MAX_VALUE elements, returns
Integer.MAX_VALUE.
Specified by:
Returns:
the number of elements in this set (its cardinality)
Returns
true if this set contains no elements.
Specified by:
Returns:
true if this set contains no elements
Returns
true if this set contains the specified element.
More formally, returns
true if and only if this set
contains an element
e such that
Objects.equals(o, e).
Specified by:
Parameters:
o - element whose presence in this set is to be tested
Returns:
true if this set contains the specified element
Throws:
Returns an iterator over the elements in this set. The elements are
returned in no particular order (unless this set is an instance of some
class that provides a guarantee).
Specified by:
Returns:
an iterator over the elements in this set
Returns an array containing all of the elements in this set.
If this set 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 will be "safe" in that no references to it
are maintained by this set. (In other words, this method must
allocate a new array even if this set is backed by an array).
The caller is thus free to modify the returned array.
This method acts as bridge between array-based and collection-based
APIs.
Specified by:
Returns:
an array containing all the elements in this set
Returns an array containing all of the elements in this set; the
runtime type of the returned array is that of the specified array.
If the set 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 set.
If this set fits in the specified array with room to spare
(i.e., the array has more elements than this set), the element in
the array immediately following the end of the set is set to
null. (This is useful in determining the length of this
set only if the caller knows that this set does not contain
any null elements.)
If this set makes any guarantees as to what order its elements
are returned by its iterator, this method must return the elements
in the same order.
Like the toArray() method, this method acts as bridge between
array-based and collection-based APIs. Further, this method allows
precise control over the runtime type of the output array, and may,
under certain circumstances, be used to save allocation costs.
Suppose x is a set known to contain only strings.
The following code can be used to dump the set into a newly allocated
array of String:
String[] y = x.toArray(new String[0]);
Note that
toArray(new Object[0]) is identical in function to
toArray().
Specified by:
Type Parameters:
T - the component type of the array to contain the collection
Parameters:
a - the array into which the elements of this set are to be
stored, if it is big enough; otherwise, a new array of the same
runtime type is allocated for this purpose.
Returns:
an array containing all the elements in this set
Throws:
ArrayStoreException - if the runtime type of the specified array
is not a supertype of the runtime type of every element in this
set
Adds the specified element to this set if it is not already present
(optional operation). More formally, adds the specified element
e to this set if the set contains no element
e2
such that
Objects.equals(e, e2).
If this set already contains the element, the call leaves the set
unchanged and returns
false. In combination with the
restriction on constructors, this ensures that sets never contain
duplicate elements.
The stipulation above does not imply that sets must accept all
elements; sets may refuse to add any particular element, including
null, and throw an exception, as described in the
specification for Collection.add.
Individual set implementations should clearly document any
restrictions on the elements that they may contain.
Specified by:
Parameters:
e - element to be added to this set
Returns:
true if this set did not already contain the specified
element
Throws:
Removes the specified element from this set if it is present
(optional operation). More formally, removes an element
e
such that
Objects.equals(o, e), if
this set contains such an element. Returns
true if this set
contained the element (or equivalently, if this set changed as a
result of the call). (This set will not contain the element once the
call returns.)
Specified by:
Parameters:
o - object to be removed from this set, if present
Returns:
true if this set contained the specified element
Throws:
Returns
true if this set contains all of the elements of the
specified collection. If the specified collection is also a set, this
method returns
true if it is a
subset of this set.
Specified by:
Parameters:
c - collection to be checked for containment in this set
Returns:
true if this set contains all of the elements of the
specified collection
Throws:
ClassCastException - if the types of one or more elements
in the specified collection are incompatible with this
set
(
optional)
NullPointerException - if the specified collection contains one
or more null elements and this set does not permit null
elements
(
optional),
or if the specified collection is null
See Also:
Adds all of the elements in the specified collection to this set if
they're not already present (optional operation). If the specified
collection is also a set, the
addAll operation effectively
modifies this set so that its value is the
union of the two
sets. The behavior of this operation is undefined if the specified
collection is modified while the operation is in progress.
Specified by:
Parameters:
c - collection containing elements to be added to this set
Returns:
true if this set changed as a result of the call
Throws:
UnsupportedOperationException - if the
addAll operation
is not supported by this set
ClassCastException - if the class of an element of the
specified collection prevents it from being added to this set
NullPointerException - if the specified collection contains one
or more null elements and this set does not permit null
elements, or if the specified collection is null
IllegalArgumentException - if some property of an element of the
specified collection prevents it from being added to this set
See Also:
Retains only the elements in this set that are contained in the
specified collection (optional operation). In other words, removes
from this set all of its elements that are not contained in the
specified collection. If the specified collection is also a set, this
operation effectively modifies this set so that its value is the
intersection of the two sets.
Specified by:
Parameters:
c - collection containing elements to be retained in this set
Returns:
true if this set changed as a result of the call
Throws:
See Also:
Removes from this set all of its elements that are contained in the
specified collection (optional operation). If the specified
collection is also a set, this operation effectively modifies this
set so that its value is the
asymmetric set difference of
the two sets.
Specified by:
Parameters:
c - collection containing elements to be removed from this set
Returns:
true if this set changed as a result of the call
Throws:
See Also:
Removes all of the elements from this set (optional operation).
The set will be empty after this call returns.
Specified by:
Throws:
Compares the specified object with this set for equality. Returns
true if the specified object is also a set, the two sets
have the same size, and every member of the specified set is
contained in this set (or equivalently, every member of this set is
contained in the specified set). This definition ensures that the
equals method works properly across different implementations of the
set interface.
Specified by:
Overrides:
Parameters:
o - object to be compared for equality with this set
Returns:
true if the specified object is equal to this set
See Also:
Returns the hash code value for this set. The hash code of a set is
defined to be the sum of the hash codes of the elements in the set,
where the hash code of a
null element is defined to be zero.
This ensures that
s1.equals(s2) implies that
s1.hashCode()==s2.hashCode() for any two sets
s1
and
s2, as required by the general contract of
Object.hashCode().
Specified by:
Overrides:
Returns:
the hash code value for this set
See Also:
Creates a
Spliterator over the elements in this set.
The Spliterator reports Spliterator.DISTINCT.
Implementations should document the reporting of additional
characteristic values.
Implementation Requirements:
The default implementation creates a
late-binding spliterator
from the set's
Iterator. The spliterator inherits the
fail-fast properties of the set's iterator.
The created Spliterator additionally reports
Spliterator.SIZED.
Implementation Note:
Specified by:
Returns:
a Spliterator over the elements in this set
Since:
1.8
Returns an unmodifiable set containing zero elements.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Returns:
an empty Set
Since:
9
Returns an unmodifiable set containing one element.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Parameters:
e1 - the single element
Returns:
a Set containing the specified element
Throws:
Since:
9
Returns an unmodifiable set containing two elements.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Parameters:
e1 - the first element
e2 - the second element
Returns:
a Set containing the specified elements
Throws:
Since:
9
Returns an unmodifiable set containing three elements.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Parameters:
e1 - the first element
e2 - the second element
e3 - the third element
Returns:
a Set containing the specified elements
Throws:
Since:
9
Returns an unmodifiable set containing four elements.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Parameters:
e1 - the first element
e2 - the second element
e3 - the third element
e4 - the fourth element
Returns:
a Set containing the specified elements
Throws:
Since:
9
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( E e1, E e2, E e3, E e4, E e5) |
Returns an unmodifiable set containing five elements.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Parameters:
e1 - the first element
e2 - the second element
e3 - the third element
e4 - the fourth element
e5 - the fifth element
Returns:
a Set containing the specified elements
Throws:
Since:
9
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( E e1, E e2, E e3, E e4, E e5, E e6) |
Returns an unmodifiable set containing six elements.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Parameters:
e1 - the first element
e2 - the second element
e3 - the third element
e4 - the fourth element
e5 - the fifth element
e6 - the sixth element
Returns:
a Set containing the specified elements
Throws:
Since:
9
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( E e1, E e2, E e3, E e4, E e5, E e6, E e7) |
Returns an unmodifiable set containing seven elements.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Parameters:
e1 - the first element
e2 - the second element
e3 - the third element
e4 - the fourth element
e5 - the fifth element
e6 - the sixth element
e7 - the seventh element
Returns:
a Set containing the specified elements
Throws:
Since:
9
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( E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) |
Returns an unmodifiable set containing eight elements.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Parameters:
e1 - the first element
e2 - the second element
e3 - the third element
e4 - the fourth element
e5 - the fifth element
e6 - the sixth element
e7 - the seventh element
e8 - the eighth element
Returns:
a Set containing the specified elements
Throws:
Since:
9
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( E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) |
Returns an unmodifiable set containing nine elements.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Parameters:
e1 - the first element
e2 - the second element
e3 - the third element
e4 - the fourth element
e5 - the fifth element
e6 - the sixth element
e7 - the seventh element
e8 - the eighth element
e9 - the ninth element
Returns:
a Set containing the specified elements
Throws:
Since:
9
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( E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) |
Returns an unmodifiable set containing ten elements.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Parameters:
e1 - the first element
e2 - the second element
e3 - the third element
e4 - the fourth element
e5 - the fifth element
e6 - the sixth element
e7 - the seventh element
e8 - the eighth element
e9 - the ninth element
e10 - the tenth element
Returns:
a Set containing the specified elements
Throws:
Since:
9
Returns an unmodifiable set containing an arbitrary number of elements.
See
Unmodifiable Sets for details.
Type Parameters:
E - the
Set's element type
Parameters:
elements - the elements to be contained in the set
Returns:
a Set containing the specified elements
Throws:
Since:
9
Returns an
unmodifiable Set containing the elements
of the given Collection. The given Collection must not be null, and it must not
contain any null elements. If the given Collection contains duplicate elements,
an arbitrary element of the duplicates is preserved. If the given Collection is
subsequently modified, the returned Set will not reflect such modifications.
Implementation Note:
If the given Collection is an
unmodifiable Set,
calling copyOf will generally not create a copy.
Type Parameters:
E - the
Set's element type
Parameters:
coll - a Collection from which elements are drawn, must be non-null
Returns:
a Set containing the elements of the given Collection
Throws:
Since:
10
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