| Modifier and Type | Class and Description |
|---|---|
static class |
SetUtils.SetView<E>
An unmodifiable view of a set that may be backed by other sets.
|
| Modifier and Type | Field and Description |
|---|---|
static SortedSet |
EMPTY_SORTED_SET
An empty unmodifiable sorted set.
|
| Modifier and Type | Method and Description |
|---|---|
static <E> SetUtils.SetView<E> |
difference(Set<? extends E> a,
Set<? extends E> b)
Returns a unmodifiable view containing the difference of the given
Sets, denoted by a \ b (or a - b). |
static <E> SetUtils.SetView<E> |
disjunction(Set<? extends E> a,
Set<? extends E> b)
Returns a unmodifiable view of the symmetric difference of the given
Sets. |
static <T> Set<T> |
emptyIfNull(Set<T> set)
Returns an immutable empty set if the argument is
null,
or the argument itself otherwise. |
static <E> Set<E> |
emptySet()
Get a typed empty unmodifiable Set.
|
static <E> SortedSet<E> |
emptySortedSet()
Get a typed empty unmodifiable sorted set.
|
static <T> int |
hashCodeForSet(Collection<T> set)
Generates a hash code using the algorithm specified in
Set.hashCode(). |
static <E> SetUtils.SetView<E> |
intersection(Set<? extends E> a,
Set<? extends E> b)
Returns a unmodifiable view of the intersection of the given
Sets. |
static boolean |
isEqualSet(Collection<?> set1,
Collection<?> set2)
Tests two sets for equality as per the
equals() contract
in Set.equals(java.lang.Object). |
static <E> Set<E> |
newIdentityHashSet()
Returns a new hash set that matches elements based on
== not
equals(). |
static <E> Set<E> |
orderedSet(Set<E> set)
Returns a set that maintains the order of elements that are added
backed by the given set.
|
static <E> SortedSet<E> |
predicatedNavigableSet(NavigableSet<E> set,
Predicate<? super E> predicate)
Returns a predicated (validating) navigable set backed by the given navigable set.
|
static <E> Set<E> |
predicatedSet(Set<E> set,
Predicate<? super E> predicate)
Returns a predicated (validating) set backed by the given set.
|
static <E> SortedSet<E> |
predicatedSortedSet(SortedSet<E> set,
Predicate<? super E> predicate)
Returns a predicated (validating) sorted set backed by the given sorted set.
|
static <E> Set<E> |
synchronizedSet(Set<E> set)
Returns a synchronized set backed by the given set.
|
static <E> SortedSet<E> |
synchronizedSortedSet(SortedSet<E> set)
Returns a synchronized sorted set backed by the given sorted set.
|
static <E> SortedSet<E> |
transformedNavigableSet(NavigableSet<E> set,
Transformer<? super E,? extends E> transformer)
Returns a transformed navigable set backed by the given navigable set.
|
static <E> Set<E> |
transformedSet(Set<E> set,
Transformer<? super E,? extends E> transformer)
Returns a transformed set backed by the given set.
|
static <E> SortedSet<E> |
transformedSortedSet(SortedSet<E> set,
Transformer<? super E,? extends E> transformer)
Returns a transformed sorted set backed by the given set.
|
static <E> SetUtils.SetView<E> |
union(Set<? extends E> a,
Set<? extends E> b)
Returns a unmodifiable view of the union of the given
Sets. |
static <E> SortedSet<E> |
unmodifiableNavigableSet(NavigableSet<E> set)
Returns an unmodifiable navigable set backed by the given navigable set.
|
static <E> Set<E> |
unmodifiableSet(Set<? extends E> set)
Returns an unmodifiable set backed by the given set.
|
static <E> SortedSet<E> |
unmodifiableSortedSet(SortedSet<E> set)
Returns an unmodifiable sorted set backed by the given sorted set.
|
public static final SortedSet EMPTY_SORTED_SET
public static <E> Set<E> emptySet()
E - the element typepublic static <E> SortedSet<E> emptySortedSet()
E - the element typepublic static <T> Set<T> emptyIfNull(Set<T> set)
null,
or the argument itself otherwise.T - the element typeset - the set, possibly nullnullpublic static boolean isEqualSet(Collection<?> set1, Collection<?> set2)
equals() contract
in Set.equals(java.lang.Object).
This method is useful for implementing Set when you cannot
extend AbstractSet. The method takes Collection instances to enable other
collection types to use the Set implementation algorithm.
The relevant text (slightly paraphrased as this is a static method) is:
Two sets are considered equal if they have the same size, and every member of the first set is contained in the second. This ensures that the
equalsmethod works properly across different implementations of theSetinterface.This implementation first checks if the two sets are the same object: if so it returns
true. Then, it checks if the two sets are identical in size; if not, it returns false. If so, it returnsa.containsAll((Collection) b).
set1 - the first set, may be nullset2 - the second set, may be nullSetpublic static <T> int hashCodeForSet(Collection<T> set)
Set.hashCode().
This method is useful for implementing Set when you cannot
extend AbstractSet. The method takes Collection instances to enable other
collection types to use the Set implementation algorithm.
T - the element typeset - the set to calculate the hash code for, may be nullSet.hashCode()public static <E> Set<E> newIdentityHashSet()
== not
equals().
This set will violate the detail of various Set contracts.
As a general rule, don't compare this set to other sets. In particular, you can't
use decorators like ListOrderedSet on it, which silently assume that these
contracts are fulfilled.
Note that the returned set is not synchronized and is not thread-safe.
If you wish to use this set from multiple threads concurrently, you must use
appropriate synchronization. The simplest approach is to wrap this map
using Collections.synchronizedSet(Set). This class may throw
exceptions when accessed by concurrent threads without synchronization.
E - the element typepublic static <E> Set<E> synchronizedSet(Set<E> set)
You must manually synchronize on the returned set's iterator to avoid non-deterministic behavior:
Set s = SetUtils.synchronizedSet(mySet);
synchronized (s) {
Iterator i = s.iterator();
while (i.hasNext()) {
process (i.next());
}
}
This method is just a wrapper for Collections.synchronizedSet(Set).E - the element typeset - the set to synchronize, must not be nullNullPointerException - if the set is nullpublic static <E> Set<E> unmodifiableSet(Set<? extends E> set)
This method uses the implementation in the decorators subpackage.
E - the element typeset - the set to make unmodifiable, must not be nullNullPointerException - if the set is nullpublic static <E> Set<E> predicatedSet(Set<E> set, Predicate<? super E> predicate)
Only objects that pass the test in the given predicate can be added to the set. Trying to add an invalid object results in an IllegalArgumentException. It is important not to use the original set after invoking this method, as it is a backdoor for adding invalid objects.
E - the element typeset - the set to predicate, must not be nullpredicate - the predicate for the set, must not be nullNullPointerException - if the set or predicate is nullpublic static <E> Set<E> transformedSet(Set<E> set, Transformer<? super E,? extends E> transformer)
Each object is passed through the transformer as it is added to the Set. It is important not to use the original set after invoking this method, as it is a backdoor for adding untransformed objects.
Existing entries in the specified set will not be transformed.
If you want that behaviour, see TransformedSet.transformedSet(java.util.Set<E>, org.apache.commons.collections4.Transformer<? super E, ? extends E>).
E - the element typeset - the set to transform, must not be nulltransformer - the transformer for the set, must not be nullNullPointerException - if the set or transformer is nullpublic static <E> Set<E> orderedSet(Set<E> set)
If an element is added twice, the order is determined by the first add. The order is observed through the iterator or toArray.
E - the element typeset - the set to order, must not be nullNullPointerException - if the set is nullpublic static <E> SortedSet<E> synchronizedSortedSet(SortedSet<E> set)
You must manually synchronize on the returned set's iterator to avoid non-deterministic behavior:
Set s = SetUtils.synchronizedSortedSet(mySet);
synchronized (s) {
Iterator i = s.iterator();
while (i.hasNext()) {
process (i.next());
}
}
This method is just a wrapper for Collections.synchronizedSortedSet(SortedSet).E - the element typeset - the sorted set to synchronize, must not be nullNullPointerException - if the set is nullpublic static <E> SortedSet<E> unmodifiableSortedSet(SortedSet<E> set)
This method uses the implementation in the decorators subpackage.
E - the element typeset - the sorted set to make unmodifiable, must not be nullNullPointerException - if the set is nullpublic static <E> SortedSet<E> predicatedSortedSet(SortedSet<E> set, Predicate<? super E> predicate)
Only objects that pass the test in the given predicate can be added to the set. Trying to add an invalid object results in an IllegalArgumentException. It is important not to use the original set after invoking this method, as it is a backdoor for adding invalid objects.
E - the element typeset - the sorted set to predicate, must not be nullpredicate - the predicate for the sorted set, must not be nullNullPointerException - if the set or predicate is nullpublic static <E> SortedSet<E> transformedSortedSet(SortedSet<E> set, Transformer<? super E,? extends E> transformer)
Each object is passed through the transformer as it is added to the Set. It is important not to use the original set after invoking this method, as it is a backdoor for adding untransformed objects.
Existing entries in the specified set will not be transformed.
If you want that behaviour, see TransformedSortedSet.transformedSortedSet(java.util.SortedSet<E>, org.apache.commons.collections4.Transformer<? super E, ? extends E>).
E - the element typeset - the set to transform, must not be nulltransformer - the transformer for the set, must not be nullNullPointerException - if the set or transformer is nullpublic static <E> SortedSet<E> unmodifiableNavigableSet(NavigableSet<E> set)
This method uses the implementation in the decorators subpackage.
E - the element typeset - the navigable set to make unmodifiable, must not be nullNullPointerException - if the set is nullpublic static <E> SortedSet<E> predicatedNavigableSet(NavigableSet<E> set, Predicate<? super E> predicate)
Only objects that pass the test in the given predicate can be added to the set. Trying to add an invalid object results in an IllegalArgumentException. It is important not to use the original set after invoking this method, as it is a backdoor for adding invalid objects.
E - the element typeset - the navigable set to predicate, must not be nullpredicate - the predicate for the navigable set, must not be nullNullPointerException - if the set or predicate is nullpublic static <E> SortedSet<E> transformedNavigableSet(NavigableSet<E> set, Transformer<? super E,? extends E> transformer)
Each object is passed through the transformer as it is added to the Set. It is important not to use the original set after invoking this method, as it is a backdoor for adding untransformed objects.
Existing entries in the specified set will not be transformed.
If you want that behaviour, see TransformedNavigableSet.transformedNavigableSet(java.util.NavigableSet<E>, org.apache.commons.collections4.Transformer<? super E, ? extends E>).
E - the element typeset - the navigable set to transform, must not be nulltransformer - the transformer for the set, must not be nullNullPointerException - if the set or transformer is nullpublic static <E> SetUtils.SetView<E> union(Set<? extends E> a, Set<? extends E> b)
Sets.
The returned view contains all elements of a and b.
E - the generic type that is able to represent the types contained
in both input sets.a - the first set, must not be nullb - the second set, must not be nullNullPointerException - if either input set is nullpublic static <E> SetUtils.SetView<E> difference(Set<? extends E> a, Set<? extends E> b)
Sets, denoted by a \ b (or a - b).
The returned view contains all elements of a that are not a member
of b.
E - the generic type that is able to represent the types contained
in both input sets.a - the set to subtract from, must not be nullb - the set to subtract, must not be nullpublic static <E> SetUtils.SetView<E> intersection(Set<? extends E> a, Set<? extends E> b)
Sets.
The returned view contains all elements that are members of both input sets
(a and b).
E - the generic type that is able to represent the types contained
in both input sets.a - the first set, must not be nullb - the second set, must not be nullpublic static <E> SetUtils.SetView<E> disjunction(Set<? extends E> a, Set<? extends E> b)
Sets.
The returned view contains all elements of a and b that are
not a member of the other set.
This is equivalent to union(difference(a, b), difference(b, a)).
E - the generic type that is able to represent the types contained
in both input sets.a - the first set, must not be nullb - the second set, must not be nullCopyright © 2001–2018 The Apache Software Foundation. All rights reserved.