boolean add(E e)
Adds the specified element to this set if it is not already present (optional operation).
boolean addAll(Collection<? extends E> c)
Adds all of the elements in the specified collection to this set if they're not already present (optional operation).
void clear()
Removes all of the elements from this set (optional operation).
boolean contains(Object o)
Returns true if this set contains the specified element.
boolean containsAll(Collection<?> c)
Returns true if this set contains all of the elements of the specified collection.
static <E> Set<E> copyOf(Collection<? extends E> coll)
Returns an
unmodifiable Setcontaining the elements of the given Collection.
boolean equals(Object o)
Compares the specified object with this set for equality.
int hashCode()
Returns the hash code value for this set.
boolean isEmpty()
Returns true if this set contains no elements.
Iterator<E> iterator()
Returns an iterator over the elements in this set.
static <E> Set<E> of()
Returns an unmodifiable set containing zero elements.
static <E> Set<E> of(E e1)
Returns an unmodifiable set containing one element.
static <E> Set<E> of(E... elements)
Returns an unmodifiable set containing an arbitrary number of elements.
static <E> Set<E> of(E e1, E e2)
Returns an unmodifiable set containing two elements.
static <E> Set<E> of(E e1, E e2, E e3)
Returns an unmodifiable set containing three elements.
static <E> Set<E> of(E e1, E e2, E e3, E e4)
Returns an unmodifiable set containing four elements.
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5)
Returns an unmodifiable set containing five elements.
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6)
Returns an unmodifiable set containing six elements.
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7)
Returns an unmodifiable set containing seven elements.
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8)
Returns an unmodifiable set containing eight elements.
static <E> Set<E> 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.
static <E> Set<E> 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.
boolean remove(Object o)
Removes the specified element from this set if it is present (optional operation).
boolean removeAll(Collection<?> c)
Removes from this set all of its elements that are contained in the specified collection (optional operation).
boolean retainAll(Collection<?> c)
Retains only the elements in this set that are contained in the specified collection (optional operation).
int size()
Returns the number of elements in this set (its cardinality).
default Spliterator<E> spliterator()
Creates a Spliterator over the elements in this set.
Object[] toArray()
Returns an array containing all of the elements in this set.
<T> T[] toArray(T[] a)
Returns an array containing all of the elements in this set; the runtime type of the returned array is that of the specified array.
parallelStream, removeIf, stream, toArrayint size()
Returns the number of elements in this set (its cardinality). If this set contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.
size in interface Collection<E>
boolean isEmpty()
Returns true if this set contains no elements.
isEmpty in interface Collection<E>
true if this set contains no elements
boolean contains(Object o)
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).
contains in interface Collection<E>
o - element whose presence in this set is to be tested
true if this set contains the specified element
ClassCastException - if the type of the specified element is incompatible with this set (optional)
NullPointerException - if the specified element is null and this set does not permit null elements (optional)
Iterator<E> iterator()
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).
Object[] toArray()
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.
toArray in interface Collection<E>
<T> T[] toArray(T[] a)
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()
.
toArray in interface Collection<E>
T - the component type of the array to contain the collection
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.
ArrayStoreException - if the runtime type of the specified array is not a supertype of the runtime type of every element in this set
NullPointerException - if the specified array is null
boolean add(E e)
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.
add in interface Collection<E>
e - element to be added to this set
true if this set did not already contain the specified element
UnsupportedOperationException - if the add operation is not supported by this set
ClassCastException - if the class of the specified element prevents it from being added to this set
NullPointerException - if the specified element is null and this set does not permit null elements
IllegalArgumentException - if some property of the specified element prevents it from being added to this set
boolean remove(Object o)
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.)
remove in interface Collection<E>
o - object to be removed from this set, if present
true if this set contained the specified element
ClassCastException - if the type of the specified element is incompatible with this set (optional)
NullPointerException - if the specified element is null and this set does not permit null elements (optional)
UnsupportedOperationException - if the remove operation is not supported by this set
boolean containsAll(Collection<?> c)
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.
containsAll in interface Collection<E>
c - collection to be checked for containment in this set
true if this set contains all of the elements of the specified collection
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
contains(Object)
boolean addAll(Collection<? extends E> c)
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.
addAll in interface Collection<E>
c - collection containing elements to be added to this set
true if this set changed as a result of the call
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
add(Object)
boolean retainAll(Collection<?> c)
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.
retainAll in interface Collection<E>
c - collection containing elements to be retained in this set
true if this set changed as a result of the call
UnsupportedOperationException - if the retainAll operation is not supported by this set
ClassCastException - if the class of an element of this set is incompatible with the specified collection (optional)
NullPointerException - if this set contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null
remove(Object)
boolean removeAll(Collection<?> c)
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.
removeAll in interface Collection<E>
c - collection containing elements to be removed from this set
true if this set changed as a result of the call
UnsupportedOperationException - if the removeAll operation is not supported by this set
ClassCastException - if the class of an element of this set is incompatible with the specified collection (optional)
NullPointerException - if this set contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null
remove(Object), contains(Object)
void clear()
Removes all of the elements from this set (optional operation). The set will be empty after this call returns.
clear in interface Collection<E>
UnsupportedOperationException - if the clear method is not supported by this set
boolean equals(Object o)
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.
equals in interface Collection<E>
equals in class Object
o - object to be compared for equality with this set
true if the specified object is equal to this set
Object.hashCode(), HashMap
int hashCode()
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()
.
hashCode in interface Collection<E>
hashCode in class Object
Object.equals(Object), equals(Object)
default Spliterator<E> spliterator()
Creates a
Spliterator
over the elements in this set.
The Spliterator reports Spliterator.DISTINCT. Implementations should document the reporting of additional characteristic values.
spliterator in interface Collection<E>
spliterator in interface Iterable<E>
Iterator. The spliterator inherits the fail-fast properties of the set's iterator.
The created Spliterator additionally reports Spliterator.SIZED.
Spliterator additionally reports Spliterator.SUBSIZED.
Spliterator over the elements in this set
static <E> Set<E> of()
Returns an unmodifiable set containing zero elements. See
Unmodifiable Setsfor details.
E - the Set's element type
Set
static <E> Set<E> of(E e1)
Returns an unmodifiable set containing one element. See
Unmodifiable Setsfor details.
E - the Set's element type
e1 - the single element
Set containing the specified element
NullPointerException - if the element is null
static <E> Set<E> of(E e1, E e2)
Returns an unmodifiable set containing two elements. See
Unmodifiable Setsfor details.
E - the Set's element type
e1 - the first element
e2 - the second element
Set containing the specified elements
IllegalArgumentException - if the elements are duplicates
NullPointerException - if an element is null
static <E> Set<E> of(E e1, E e2, E e3)
Returns an unmodifiable set containing three elements. See
Unmodifiable Setsfor details.
E - the Set's element type
e1 - the first element
e2 - the second element
e3 - the third element
Set containing the specified elements
IllegalArgumentException - if there are any duplicate elements
NullPointerException - if an element is null
static <E> Set<E> of(E e1, E e2, E e3, E e4)
Returns an unmodifiable set containing four elements. See
Unmodifiable Setsfor details.
E - the Set's element type
e1 - the first element
e2 - the second element
e3 - the third element
e4 - the fourth element
Set containing the specified elements
IllegalArgumentException - if there are any duplicate elements
NullPointerException - if an element is null
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5)
Returns an unmodifiable set containing five elements. See
Unmodifiable Setsfor details.
E - the Set's element type
e1 - the first element
e2 - the second element
e3 - the third element
e4 - the fourth element
e5 - the fifth element
Set containing the specified elements
IllegalArgumentException - if there are any duplicate elements
NullPointerException - if an element is null
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6)
Returns an unmodifiable set containing six elements. See
Unmodifiable Setsfor details.
E - the Set's element type
e1 - the first element
e2 - the second element
e3 - the third element
e4 - the fourth element
e5 - the fifth element
e6 - the sixth element
Set containing the specified elements
IllegalArgumentException - if there are any duplicate elements
NullPointerException - if an element is null
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7)
Returns an unmodifiable set containing seven elements. See
Unmodifiable Setsfor details.
E - the Set's element type
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
Set containing the specified elements
IllegalArgumentException - if there are any duplicate elements
NullPointerException - if an element is null
static <E> Set<E> of(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 Setsfor details.
E - the Set's element type
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
Set containing the specified elements
IllegalArgumentException - if there are any duplicate elements
NullPointerException - if an element is null
static <E> Set<E> 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. See
Unmodifiable Setsfor details.
E - the Set's element type
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
Set containing the specified elements
IllegalArgumentException - if there are any duplicate elements
NullPointerException - if an element is null
static <E> Set<E> 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. See
Unmodifiable Setsfor details.
E - the Set's element type
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
Set containing the specified elements
IllegalArgumentException - if there are any duplicate elements
NullPointerException - if an element is null
@SafeVarargs static <E> Set<E> of(E... elements)
Returns an unmodifiable set containing an arbitrary number of elements. See
Unmodifiable Setsfor details.
String[] array = ... ;
Set<String[]> list = Set.<String[]>of(array);
Set.of(E) method to be invoked instead.
E - the Set's element type
elements - the elements to be contained in the set
Set containing the specified elements
IllegalArgumentException - if there are any duplicate elements
NullPointerException - if an element is null or if the array is null
static <E> Set<E> copyOf(Collection<? extends E> coll)
Returns an
unmodifiable Setcontaining 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.
E - the Set's element type
coll - a Collection from which elements are drawn, must be non-null
Set containing the elements of the given Collection
NullPointerException - if coll is null, or if it contains any nulls
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