Package com.google.common.collect

Class ImmutableSet<E>

java.lang.Object

java.util.AbstractCollection<E>

com.google.common.collect.ImmutableCollection<E>

com.google.common.collect.ImmutableSet<E>

All Implemented Interfaces:

Serializable, Iterable<E>, Collection<E>, Set<E>

Direct Known Subclasses:

ImmutableSortedSet

@GwtCompatible(serializable=true,
               emulated=true)
public abstract class ImmutableSet<E>
extends ImmutableCollection<E>
implements Set<E>

A Set whose contents will never change, with many other important properties detailed at ImmutableCollection.

Since:

2.0

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ImmutableSet.Builder<E>	A builder for creating ImmutableSet instances.

Method Summary

Modifier and Type	Method	Description
static <E> ImmutableSet.Builder<E>	builder()	Returns a new builder.
static <E> ImmutableSet.Builder<E>	builderWithExpectedSize(int expectedSize)	Returns a new builder, expecting the specified number of distinct elements to be added.
static <E> ImmutableSet<E>	copyOf(E[] elements)	Returns an immutable set containing each of elements, minus duplicates, in the order each appears first in the source array.
static <E> ImmutableSet<E>	copyOf(Iterable<? extends E> elements)	Returns an immutable set containing each of elements, minus duplicates, in the order each appears first in the source iterable.
static <E> ImmutableSet<E>	copyOf(Collection<? extends E> elements)	Returns an immutable set containing each of elements, minus duplicates, in the order each appears first in the source collection.
static <E> ImmutableSet<E>	copyOf(Iterator<? extends E> elements)	Returns an immutable set containing each of elements, minus duplicates, in the order each appears first in the source iterator.
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 element.
static <E> ImmutableSet<E>	of(E e1, E e2)	Returns an immutable set containing the given elements, minus duplicates, in the order each was first specified.
static <E> ImmutableSet<E>	of(E e1, E e2, E e3)	Returns an immutable set containing the given elements, minus duplicates, in the order each was first specified.
static <E> ImmutableSet<E>	of(E e1, E e2, E e3, E e4)	Returns an immutable set containing the given elements, minus duplicates, in the order each was first specified.
static <E> ImmutableSet<E>	of(E e1, E e2, E e3, E e4, E e5)	Returns an immutable set containing the given elements, minus duplicates, in the order each was first specified.
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, minus duplicates, in the order each was first specified.
static <E> Collector<E,?,ImmutableSet<E>>	toImmutableSet()	Returns a Collector that accumulates the input elements into a new ImmutableSet.

Methods inherited from class com.google.common.collect.ImmutableCollection

add, addAll, asList, clear, contains, remove, removeAll, removeIf, retainAll, spliterator, toArray, toArray

Methods inherited from class java.util.AbstractCollection

containsAll, isEmpty, size, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Collection

parallelStream, removeIf, stream, toArray

Methods inherited from interface java.lang.Iterable

forEach

Methods inherited from interface java.util.Set

add, addAll, clear, contains, containsAll, isEmpty, remove, removeAll, retainAll, size, spliterator, toArray, toArray

Method Detail

toImmutableSet

public static <E> Collector<E,?,ImmutableSet<E>> toImmutableSet()

Returns a Collector that accumulates the input elements into a new ImmutableSet. Elements appear in the resulting set in the encounter order of the stream; if the stream contains duplicates (according to Object.equals(Object)), only the first duplicate in encounter order will appear in the result.

Since:

21.0

of

public static <E> ImmutableSet<E> of()

Returns the empty immutable set. Preferred over Collections.emptySet() for code consistency, and because the return type conveys the immutability guarantee.

Performance note: the instance returned is a singleton.

Type Parameters:

E - the Set's element type

Returns:

an empty Set

of

public static <E> ImmutableSet<E> of(E element)

Returns an immutable set containing element. Preferred over Collections.singleton(T) for code consistency, null rejection, and because the return type conveys the immutability guarantee.

Type Parameters:

E - the Set's element type

Parameters:

element - the single element

Returns:

a Set containing the specified element

of

public static <E> ImmutableSet<E> of(E e1,
                                     E e2)

Returns an immutable set containing the given elements, minus duplicates, in the order each was first specified. That is, if multiple elements are equal, all except the first are ignored.

Type Parameters:

E - the Set's element type

Parameters:

e1 - the first element

e2 - the second element

Returns:

a Set containing the specified elements

of

public static <E> ImmutableSet<E> of(E e1,
                                     E e2,
                                     E e3)

Returns an immutable set containing the given elements, minus duplicates, in the order each was first specified. That is, if multiple elements are equal, all except the first are ignored.

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

of

public static <E> ImmutableSet<E> of(E e1,
                                     E e2,
                                     E e3,
                                     E e4)

Returns an immutable set containing the given elements, minus duplicates, in the order each was first specified. That is, if multiple elements are equal, all except the first are ignored.

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

of

public static <E> ImmutableSet<E> of(E e1,
                                     E e2,
                                     E e3,
                                     E e4,
                                     E e5)

Returns an immutable set containing the given elements, minus duplicates, in the order each was first specified. That is, if multiple elements are equal, all except the first are ignored.

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

of

@SafeVarargs
public 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, minus duplicates, in the order each was first specified. That is, if multiple elements are equal, all except the first are ignored.

The array others must not be longer than Integer.MAX_VALUE - 6.

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

others - the seventh element

Returns:

a Set containing the specified elements

Since:

3.0 (source-compatible since 2.0)

copyOf

public static <E> ImmutableSet<E> copyOf(Collection<? extends E> elements)

Returns an immutable set containing each of elements, minus duplicates, in the order each appears first in the source collection.

Performance note: This method will sometimes recognize that the actual copy operation is unnecessary; for example, copyOf(copyOf(anArrayList)) will copy the data only once. This reduces the expense of habitually making defensive copies at API boundaries. However, the precise conditions for skipping the copy operation are undefined.

Type Parameters:

E - the Set's element type

Parameters:

elements - a Collection from which elements are drawn, must be non-null

Returns:

a Set containing the elements of the given Collection

Throws:

NullPointerException - if any of elements is null

Since:

7.0 (source-compatible since 2.0)

copyOf

public static <E> ImmutableSet<E> copyOf(Iterable<? extends E> elements)

Returns an immutable set containing each of elements, minus duplicates, in the order each appears first in the source iterable. This method iterates over elements only once.

Performance note: This method will sometimes recognize that the actual copy operation is unnecessary; for example, copyOf(copyOf(anArrayList)) should copy the data only once. This reduces the expense of habitually making defensive copies at API boundaries. However, the precise conditions for skipping the copy operation are undefined.

Throws:

NullPointerException - if any of elements is null

copyOf

public static <E> ImmutableSet<E> copyOf(Iterator<? extends E> elements)

Returns an immutable set containing each of elements, minus duplicates, in the order each appears first in the source iterator.

Throws:

NullPointerException - if any of elements is null

copyOf

public static <E> ImmutableSet<E> copyOf(E[] elements)

Returns an immutable set containing each of elements, minus duplicates, in the order each appears first in the source array.

Throws:

NullPointerException - if any of elements is null

Since:

3.0

equals

public boolean equals(@CheckForNull
                      Object object)

Description copied from class: java.lang.Object

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

• It is reflexive: for any non-null reference value x, x.equals(x) should return true.
• It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
• It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
• It is consistent: for any non-null reference values 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.
• For any non-null reference value 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.

Specified by:

equals in interface Collection<E>

Specified by:

equals in interface Set<E>

Overrides:

equals in class Object

Parameters:

object - the reference object with which to compare.

Returns:

true if this object is the same as the obj argument; false otherwise.

See Also:

Object.hashCode(), HashMap

hashCode

public int hashCode()

Description copied from class: java.lang.Object

Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

The general contract of hashCode is:

• Whenever it is invoked on the same object more than once during an execution of a Java application, the 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.
• If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
• It is not required that if two objects are unequal according to the 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. (The hashCode may or may not be implemented as some function of an object's memory address at some point in time.)

Specified by:

hashCode in interface Collection<E>

Specified by:

hashCode in interface Set<E>

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

See Also:

Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

iterator

public abstract UnmodifiableIterator<E> iterator()

Description copied from class: ImmutableCollection

Returns an unmodifiable iterator across the elements in this collection.

Specified by:

iterator in interface Collection<E>

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface Set<E>

Specified by:

iterator in class ImmutableCollection<E>

Returns:

an iterator over the elements contained in this collection

builder

public static <E> ImmutableSet.Builder<E> builder()

Returns a new builder. The generated builder is equivalent to the builder created by the ImmutableSet.Builder constructor.

builderWithExpectedSize

@Beta
public static <E> ImmutableSet.Builder<E> builderWithExpectedSize(int expectedSize)

Returns a new builder, expecting the specified number of distinct elements to be added.

If expectedSize is exactly the number of distinct elements added to the builder before ImmutableSet.Builder.build() is called, the builder is likely to perform better than an unsized builder() would have.

It is not specified if any performance benefits apply if expectedSize is close to, but not exactly, the number of distinct elements added to the builder.

Since:

23.1