@GwtCompatible(serializable=true, emulated=true) public abstract class ImmutableSet<E> extends ImmutableCollection<E> implements Set<E>
Set with reliable, user-specified
iteration order. Does not permit null elements.
Unlike Collections.unmodifiableSet(java.util.Set<? extends T>), which is a view of a
separate collection that can still change, an instance of this class contains
its own private data and will never change. This class is convenient
for public static final sets ("constant sets") and also lets you
easily make a "defensive copy" of a set provided to your class by a caller.
Warning: Like most sets, an ImmutableSet will not function
correctly if an element is modified after being placed in the set. For this
reason, and to avoid general confusion, it is strongly recommended to place
only immutable objects into this collection.
This class has been observed to perform significantly better than HashSet for objects with very fast Object.hashCode() implementations
(as a well-behaved immutable object should). While this class's factory
methods create hash-based instances, the ImmutableSortedSet subclass
performs binary searches instead.
Note: Although this class is not final, it cannot be subclassed outside its package as it has no public or protected constructors. Thus, instances of this type are guaranteed to be immutable.
See the Guava User Guide article on immutable collections.
ImmutableList,
ImmutableMap,
Serialized Form| Modifier and Type | Class and Description |
|---|---|
static class |
ImmutableSet.Builder<E>
A builder for creating immutable set instances, especially
public
static final sets ("constant sets"). |
| Modifier and Type | Method and Description |
|---|---|
static <E> ImmutableSet.Builder<E> |
builder()
Returns a new builder.
|
static <E> ImmutableSet<E> |
copyOf(Collection<? extends E> elements)
Returns an immutable set containing the given elements, in order.
|
static <E> ImmutableSet<E> |
copyOf(E[] elements)
Returns an immutable set containing the given elements, in order.
|
static <E> ImmutableSet<E> |
copyOf(Iterable<? extends E> elements)
Returns an immutable set containing the given elements, in order.
|
static <E> ImmutableSet<E> |
copyOf(Iterator<? extends E> elements)
Returns an immutable set containing the given elements, in order.
|
boolean |
equals(Object object)
Indicates whether some other object is "equal to" this one.
|
int |
hashCode()
Returns a hash code value for the object.
|
abstract UnmodifiableIterator<E> |
iterator()
Returns an unmodifiable iterator across the elements in this collection.
|
static <E> ImmutableSet<E> |
of()
Returns the empty immutable set.
|
static <E> ImmutableSet<E> |
of(E element)
Returns an immutable set containing a single element.
|
static <E> ImmutableSet<E> |
of(E e1,
E e2)
Returns an immutable set containing the given elements, in order.
|
static <E> ImmutableSet<E> |
of(E e1,
E e2,
E e3)
Returns an immutable set containing the given elements, in order.
|
static <E> ImmutableSet<E> |
of(E e1,
E e2,
E e3,
E e4)
Returns an immutable set containing the given elements, in order.
|
static <E> ImmutableSet<E> |
of(E e1,
E e2,
E e3,
E e4,
E e5)
Returns an immutable set containing the given elements, in order.
|
static <E> ImmutableSet<E> |
of(E e1,
E e2,
E e3,
E e4,
E e5,
E e6,
E... others)
Returns an immutable set containing the given elements, in order.
|
add, addAll, asList, clear, contains, remove, removeAll, retainAll, toArray, toArraycontainsAll, isEmpty, size, toStringpublic static <E> ImmutableSet<E> of()
Collections.emptySet(), and is preferable mainly for consistency
and maintainability of your code.public static <E> ImmutableSet<E> of(E element)
Collections.singleton(T), but will not accept
a null element. It is preferable mainly for consistency and
maintainability of your code.public static <E> ImmutableSet<E> of(E e1, E e2)
Object.equals(java.lang.Object)) after the
first are ignored.NullPointerException - if any element is nullpublic static <E> ImmutableSet<E> of(E e1, E e2, E e3)
Object.equals(java.lang.Object)) after the
first are ignored.NullPointerException - if any element is nullpublic static <E> ImmutableSet<E> of(E e1, E e2, E e3, E e4)
Object.equals(java.lang.Object)) after the
first are ignored.NullPointerException - if any element is nullpublic static <E> ImmutableSet<E> of(E e1, E e2, E e3, E e4, E e5)
Object.equals(java.lang.Object)) after the
first are ignored.NullPointerException - if any element is nullpublic static <E> ImmutableSet<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E... others)
Object.equals(java.lang.Object)) after the
first are ignored.NullPointerException - if any element is nullpublic static <E> ImmutableSet<E> copyOf(E[] elements)
Object.equals(java.lang.Object)) after the
first are ignored.NullPointerException - if any of elements is nullpublic static <E> ImmutableSet<E> copyOf(Iterable<? extends E> elements)
Object.equals(java.lang.Object)) after the
first are ignored. This method iterates over elements at most once.
Note that if s is a Set<String>, then ImmutableSet.copyOf(s) returns an ImmutableSet<String> containing
each of the strings in s, while ImmutableSet.of(s) returns
a ImmutableSet<Set<String>> containing one element (the given set
itself).
Despite the method name, this method attempts to avoid actually copying the data when it is safe to do so. The exact circumstances under which a copy will or will not be performed are undocumented and subject to change.
NullPointerException - if any of elements is nullpublic static <E> ImmutableSet<E> copyOf(Iterator<? extends E> elements)
Object.equals(java.lang.Object)) after the
first are ignored.NullPointerException - if any of elements is nullpublic static <E> ImmutableSet<E> copyOf(Collection<? extends E> elements)
Object.equals(java.lang.Object)) after the
first are ignored. This method iterates over elements at most
once.
Note that if s is a Set<String>, then ImmutableSet.copyOf(s) returns an ImmutableSet<String> containing
each of the strings in s, while ImmutableSet.of(s) returns
a ImmutableSet<Set<String>> containing one element (the given set
itself).
Note: Despite what the method name suggests, copyOf will
return constant-space views, rather than linear-space copies, of some
inputs known to be immutable. For some other immutable inputs, such as key
sets of an ImmutableMap, it still performs a copy in order to avoid
holding references to the values of the map. The heuristics used in this
decision are undocumented and subject to change except that:
ImmutableSortedSet.ImmutableSet.copyOf() is idempotent with respect to pointer
equality.This method is safe to use even when elements is a synchronized
or concurrent collection that is currently being modified by another
thread.
NullPointerException - if any of elements is nullpublic boolean equals(@Nullable Object object)
java.lang.Object
The equals method implements an equivalence relation
on non-null object references:
x, x.equals(x) should return
true.
x and y, x.equals(y)
should return true if and only if
y.equals(x) returns true.
x, y, and z, if
x.equals(y) returns true and
y.equals(z) returns true, then
x.equals(z) should return true.
x and y, multiple invocations of
x.equals(y) consistently return true
or consistently return false, provided no
information used in equals comparisons on the
objects is modified.
x,
x.equals(null) should return false.
The equals method for class Object implements
the most discriminating possible equivalence relation on objects;
that is, for any non-null reference values x and
y, this method returns true if and only
if x and y refer to the same object
(x == y has the value true).
Note that it is generally necessary to override the hashCode
method whenever this method is overridden, so as to maintain the
general contract for the hashCode method, which states
that equal objects must have equal hash codes.
equals in interface Collection<E>equals in interface Set<E>equals in class Objectobject - the reference object with which to compare.true if this object is the same as the obj
argument; false otherwise.Object.hashCode(),
HashMappublic int hashCode()
java.lang.ObjectHashMap.
The general contract of hashCode is:
hashCode method
must consistently return the same integer, provided no information
used in equals comparisons on the object is modified.
This integer need not remain consistent from one execution of an
application to another execution of the same application.
equals(Object)
method, then calling the hashCode method on each of
the two objects must produce the same integer result.
Object.equals(java.lang.Object)
method, then calling the hashCode method on each of the
two objects must produce distinct integer results. However, the
programmer should be aware that producing distinct integer results
for unequal objects may improve the performance of hash tables.
As much as is reasonably practical, the hashCode method defined by
class Object does return distinct integers for distinct
objects. (This is typically implemented by converting the internal
address of the object into an integer, but this implementation
technique is not required by the
JavaTM programming language.)
hashCode in interface Collection<E>hashCode in interface Set<E>hashCode in class ObjectObject.equals(java.lang.Object),
System.identityHashCode(java.lang.Object)public abstract UnmodifiableIterator<E> iterator()
ImmutableCollectionpublic static <E> ImmutableSet.Builder<E> builder()
ImmutableSet.Builder constructor.Copyright © 2010-2013. All Rights Reserved.