java.lang.Object
- java.util.AbstractCollection<E>
- - com.google.common.collect.ImmutableCollection<E>
  - - com.google.common.collect.ImmutableSet<E>

All Implemented Interfaces:

java.io.Serializable, java.lang.Iterable<E>, java.util.Collection<E>, java.util.Set<E>

Direct Known Subclasses:

ImmutableEnumSet, ImmutableMapEntrySet, ImmutableSet.Indexed, ImmutableSetMultimap.EntrySet, ImmutableSortedSetFauxverideShim, IndexedImmutableSet, RegularImmutableSet, SingletonImmutableSet
```
public abstract class ImmutableSet<E>
extends ImmutableCollection<E>
implements java.util.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.
`(package private) static class`	`ImmutableSet.Indexed<E>`
`private static class`	`ImmutableSet.JdkBackedSetBuilderImpl<E>`	SetBuilderImpl version that uses a JDK HashSet, which has built in hash flooding protection.
`private static class`	`ImmutableSet.RegularSetBuilderImpl<E>`	Default implementation of the guts of ImmutableSet.Builder, creating an open-addressed hash table and deduplicating elements as they come, so it only allocates O(max(distinct, expectedCapacity)) rather than O(calls to add).
`private static class`	`ImmutableSet.SerializedForm`
`private static class`	`ImmutableSet.SetBuilderImpl<E>`	Swappable internal implementation of an ImmutableSet.Builder.

Field Summary

Fields
Modifier and Type	Field	Description
`private ImmutableList<E>`	`asList`
`private static int`	`CUTOFF`
`private static double`	`DESIRED_LOAD_FACTOR`
`(package private) static double`	`HASH_FLOODING_FPP`	We attempt to detect deliberate hash flooding attempts, and if one is detected, fall back to a wrapper around j.u.HashSet, which has built in flooding protection.
`(package private) static int`	`MAX_RUN_MULTIPLIER`
`(package private) static int`	`MAX_TABLE_SIZE`
`(package private) static int`	`SPLITERATOR_CHARACTERISTICS`

Constructor Summary

Constructors
Constructor Description

ImmutableSet()

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`ImmutableList<E>`	`asList()`	Returns an `ImmutableList` containing the same elements, in the same order, as this collection.
`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.
`(package private) static int`	`chooseTableSize(int setSize)`	Returns an array size suitable for the backing array of a hash table that uses open addressing with linear probing in its implementation.
`private static <E> ImmutableSet<E>`	`construct(int n, int expectedSize, java.lang.Object... elements)`	Constructs an `ImmutableSet` from the first `n` elements of the specified array.
`private static <E> ImmutableSet<E>`	`constructUnknownDuplication(int n, java.lang.Object... elements)`	Constructs an `ImmutableSet` from the first `n` elements of the specified array, which we have no particular reason to believe does or does not contain duplicates.
`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(java.lang.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(java.util.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(java.util.Iterator<? extends E> elements)`	Returns an immutable set containing each of `elements`, minus duplicates, in the order each appears first in the source iterator.
`private static ImmutableSet`	`copyOfEnumSet(java.util.EnumSet enumSet)`
`(package private) ImmutableList<E>`	`createAsList()`
`boolean`	`equals(java.lang.Object object)`
`int`	`hashCode()`
`(package private) static boolean`	`hashFloodingDetected(java.lang.Object[] hashTable)`	Checks the whole hash table for poor hash distribution.
`(package private) boolean`	`isHashCodeFast()`	Returns `true` if the `hashCode()` method runs quickly.
`abstract UnmodifiableIterator<E>`	`iterator()`	Returns an unmodifiable iterator across the elements in this collection.
`private static int`	`maxRunBeforeFallback(int tableSize)`	If more than this many consecutive positions are filled in a table of the specified size, report probable hash flooding.
`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.
`(package private) static java.lang.Object[]`	`rebuildHashTable(int newTableSize, java.lang.Object[] elements, int n)`	Builds a new open-addressed hash table from the first n objects in elements.
`static <E> java.util.stream.Collector<E,?,ImmutableSet<E>>`	`toImmutableSet()`	Returns a `Collector` that accumulates the input elements into a new `ImmutableSet`.
`(package private) java.lang.Object`	`writeReplace()`

Methods inherited from class com.google.common.collect.ImmutableCollection
add, addAll, clear, contains, copyIntoArray, internalArray, internalArrayEnd, internalArrayStart, isPartialView, 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

- Field Detail
  - SPLITERATOR_CHARACTERISTICS
```
static final int SPLITERATOR_CHARACTERISTICS
```
    See Also:
    
    Constant Field Values
  - asList
```
private transient ImmutableList<E> asList
```
  - MAX_TABLE_SIZE
```
static final int MAX_TABLE_SIZE
```
    See Also:
    
    Constant Field Values
  - DESIRED_LOAD_FACTOR
```
private static final double DESIRED_LOAD_FACTOR
```
    See Also:
    
    Constant Field Values
  - CUTOFF
```
private static final int CUTOFF
```
    See Also:
    
    Constant Field Values
  - HASH_FLOODING_FPP
```
static final double HASH_FLOODING_FPP
```
    We attempt to detect deliberate hash flooding attempts, and if one is detected, fall back to a wrapper around j.u.HashSet, which has built in flooding protection. HASH_FLOODING_FPP is the maximum allowed probability of falsely detecting a hash flooding attack if the input is randomly generated.
    MAX_RUN_MULTIPLIER was determined experimentally to match this FPP.
    
    See Also:
    
    Constant Field Values
  - MAX_RUN_MULTIPLIER
```
static final int MAX_RUN_MULTIPLIER
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - ImmutableSet
```
ImmutableSet()
```
- Method Detail
  - toImmutableSet
```
public static <E> java.util.stream.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.
  - 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.
  - 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.
  - 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.
  - 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.
  - 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.
  - 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.
    
    Since:
    
    3.0 (source-compatible since 2.0)
  - constructUnknownDuplication
```
private static <E> ImmutableSet<E> constructUnknownDuplication(int n,
                                                               java.lang.Object... elements)
```
    Constructs an ImmutableSet from the first n elements of the specified array, which we have no particular reason to believe does or does not contain duplicates. If k is the size of the returned ImmutableSet, then the unique elements of elements will be in the first k positions, and elements[i] == null for k <= i < n.
    This may modify elements. Additionally, if n == elements.length and elements contains no duplicates, elements may be used without copying in the returned ImmutableSet, in which case the caller must not modify it.
    elements may contain only values of type E.
    
    Throws:
    
    java.lang.NullPointerException - if any of the first n elements of elements is null
  - construct
```
private static <E> ImmutableSet<E> construct(int n,
                                             int expectedSize,
                                             java.lang.Object... elements)
```
    Constructs an ImmutableSet from the first n elements of the specified array. If k is the size of the returned ImmutableSet, then the unique elements of elements will be in the first k positions, and elements[i] == null for k <= i < n.
    This may modify elements. Additionally, if n == elements.length and elements contains no duplicates, elements may be used without copying in the returned ImmutableSet, in which case it may no longer be modified.
    elements may contain only values of type E.
    
    Throws:
    
    java.lang.NullPointerException - if any of the first n elements of elements is null
  - copyOf
```
public static <E> ImmutableSet<E> copyOf(java.util.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.
    
    Throws:
    
    java.lang.NullPointerException - if any of elements is null
    
    Since:
    
    7.0 (source-compatible since 2.0)
  - copyOf
```
public static <E> ImmutableSet<E> copyOf(java.lang.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:
    
    java.lang.NullPointerException - if any of elements is null
  - copyOf
```
public static <E> ImmutableSet<E> copyOf(java.util.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:
    
    java.lang.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:
    
    java.lang.NullPointerException - if any of elements is null
    
    Since:
    
    3.0
  - copyOfEnumSet
```
private static ImmutableSet copyOfEnumSet(java.util.EnumSet enumSet)
```
  - isHashCodeFast
```
boolean isHashCodeFast()
```
    Returns true if the hashCode() method runs quickly.
  - equals
```
public boolean equals(java.lang.Object object)
```
    Specified by:
    
    equals in interface java.util.Collection<E>
    
    Specified by:
    
    equals in interface java.util.Set<E>
    
    Overrides:
    
    equals in class java.lang.Object
  - hashCode
```
public int hashCode()
```
    Specified by:
    
    hashCode in interface java.util.Collection<E>
    
    Specified by:
    
    hashCode in interface java.util.Set<E>
    
    Overrides:
    
    hashCode in class 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 java.util.Collection<E>
    
    Specified by:
    
    iterator in interface java.lang.Iterable<E>
    
    Specified by:
    
    iterator in interface java.util.Set<E>
    
    Specified by:
    
    iterator in class ImmutableCollection<E>
  - asList
```
public ImmutableList<E> asList()
```
    Description copied from class: ImmutableCollection
    
    Returns an ImmutableList containing the same elements, in the same order, as this collection.
    Performance note: in most cases this method can return quickly without actually copying anything. The exact circumstances under which the copy is performed are undefined and subject to change.
    
    Overrides:
    
    asList in class ImmutableCollection<E>
  - createAsList
```
ImmutableList<E> createAsList()
```
  - writeReplace
```
java.lang.Object writeReplace()
```
    Overrides:
    
    writeReplace in class ImmutableCollection<E>
  - 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
```
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
  - rebuildHashTable
```
static java.lang.Object[] rebuildHashTable(int newTableSize,
                                           java.lang.Object[] elements,
                                           int n)
```
    Builds a new open-addressed hash table from the first n objects in elements.
  - chooseTableSize
```
static int chooseTableSize(int setSize)
```
    Returns an array size suitable for the backing array of a hash table that uses open addressing with linear probing in its implementation. The returned size is the smallest power of two that can hold setSize elements with the desired load factor. Always returns at least setSize + 2.
  - hashFloodingDetected
```
static boolean hashFloodingDetected(java.lang.Object[] hashTable)
```
    Checks the whole hash table for poor hash distribution. Takes O(n) in the worst case, O(n / log n) on average.
    The online hash flooding detecting in RegularSetBuilderImpl.add can detect e.g. many exactly matching hash codes, which would cause construction to take O(n^2), but can't detect e.g. hash codes adversarially designed to go into ascending table locations, which keeps construction O(n) (as desired) but then can have O(n) queries later.
    If this returns false, then no query can take more than O(log n).
    Note that for a RegularImmutableSet with elements with truly random hash codes, contains operations take expected O(1) time but with high probability take O(log n) for at least some element. (https://en.wikipedia.org/wiki/Linear_probing#Analysis)
    This method may return true up to HASH_FLOODING_FPP of the time even on truly random input.
    If this method returns false, there are definitely no runs of length at least maxRunBeforeFallback(hashTable.length) nonnull elements. If there are no runs of length at least maxRunBeforeFallback(hashTable.length) / 2 nonnull elements, this method definitely returns false. In between those constraints, the result of this method is undefined, subject to the above HASH_FLOODING_FPP constraint.
  - maxRunBeforeFallback
```
private static int maxRunBeforeFallback(int tableSize)
```
    If more than this many consecutive positions are filled in a table of the specified size, report probable hash flooding. (hashFloodingDetected(java.lang.Object[]) may also report hash flooding if fewer consecutive positions are filled; see that method for details.)

Class ImmutableSet<E>

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

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

Methods inherited from class java.util.AbstractCollection

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Collection

Methods inherited from interface java.lang.Iterable

Methods inherited from interface java.util.Set

Field Detail

SPLITERATOR_CHARACTERISTICS

asList

MAX_TABLE_SIZE

DESIRED_LOAD_FACTOR

CUTOFF

HASH_FLOODING_FPP

MAX_RUN_MULTIPLIER

Constructor Detail

ImmutableSet

Method Detail

toImmutableSet

of

of

of

of

of

of

of

constructUnknownDuplication

construct

copyOf

copyOf

copyOf

copyOf

copyOfEnumSet

isHashCodeFast

equals

hashCode

iterator

asList

createAsList

writeReplace

builder

builderWithExpectedSize

rebuildHashTable

chooseTableSize

hashFloodingDetected

maxRunBeforeFallback