Package org.docx4j.com.google.common.collect

Class ImmutableSet<E>

java.lang.Object

java.util.AbstractCollection<E>

org.docx4j.com.google.common.collect.ImmutableCollection<E>

org.docx4j.com.google.common.collect.ImmutableSet<E>

All Implemented Interfaces:

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

Direct Known Subclasses:

RegularImmutableSet, SingletonImmutableSet

@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.
private static final class	ImmutableSet.JdkBackedSetBuilderImpl<E>	SetBuilderImpl version that uses a JDK HashSet, which has built in hash flooding protection.
private static final 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 static final int	CUTOFF
private static final double	DESIRED_LOAD_FACTOR
(package private) 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.
(package private) static final int	MAX_RUN_MULTIPLIER
(package private) static final int	MAX_TABLE_SIZE
(package private) static final int	SPLITERATOR_CHARACTERISTICS

Constructor Summary

Constructors

Constructor	Description
ImmutableSet()

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.
(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, Object... elements)	Constructs an ImmutableSet from the first n elements of the specified array.
private static <E> ImmutableSet<E>	constructUnknownDuplication(int n, 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(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(@Nullable Object object)
int	hashCode()
(package private) static boolean	hashFloodingDetected(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 Object[]	rebuildHashTable(int newTableSize, Object[] elements, int n)	Builds a new open-addressed hash table from the first n objects in elements.
(package private) Object	writeReplace()

Methods inherited from class org.docx4j.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 Details

SPLITERATOR_CHARACTERISTICS

static final int SPLITERATOR_CHARACTERISTICS

See Also:

• Constant Field Values

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 Details

ImmutableSet

ImmutableSet()

Method Details

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,
 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:

NullPointerException - if any of the first n elements of elements is null

construct

private static <E> ImmutableSet<E> construct(int n,
 int expectedSize,
 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:

NullPointerException - if any of the first n elements of elements is null

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.

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

isHashCodeFast

boolean isHashCodeFast()

Returns true if the hashCode() method runs quickly.

equals

public boolean equals(@Nullable Object object)

Specified by:

equals in interface Collection<E>

Specified by:

equals in interface Set<E>

Overrides:

equals in class Object

hashCode

public int hashCode()

Specified by:

hashCode in interface Collection<E>

Specified by:

hashCode in interface Set<E>

Overrides:

hashCode in class 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>

writeReplace

Object writeReplace()

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

rebuildHashTable

static Object[] rebuildHashTable(int newTableSize,
 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(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.)