eaglercraft-1.8/sources/main/java/com/google/common/collect/ImmutableSet.java

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/*
* Copyright (C) 2007 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.collect;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.collect.ObjectArrays.checkElementNotNull;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.EnumSet;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import javax.annotation.Nullable;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.primitives.Ints;
/**
* A high-performance, immutable {@code Set} with reliable, user-specified
* iteration order. Does not permit null elements.
*
* <p>
* Unlike {@link Collections#unmodifiableSet}, which is a <i>view</i> of a
* separate collection that can still change, an instance of this class contains
* its own private data and will <i>never</i> change. This class is convenient
* for {@code 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.
*
* <p>
* <b>Warning:</b> Like most sets, an {@code 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.
*
* <p>
* This class has been observed to perform significantly better than
* {@link HashSet} for objects with very fast {@link Object#hashCode}
* implementations (as a well-behaved immutable object should). While this
* class's factory methods create hash-based instances, the
* {@link ImmutableSortedSet} subclass performs binary searches instead.
*
* <p>
* <b>Note:</b> 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.
*
* <p>
* See the Guava User Guide article on <a href=
* "http://code.google.com/p/guava-libraries/wiki/ImmutableCollectionsExplained">
* immutable collections</a>.
*
* @see ImmutableList
* @see ImmutableMap
* @author Kevin Bourrillion
* @author Nick Kralevich
* @since 2.0 (imported from Google Collections Library)
*/
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableSet<E> extends ImmutableCollection<E> implements Set<E> {
/**
* Returns the empty immutable set. This set behaves and performs comparably to
* {@link Collections#emptySet}, and is preferable mainly for consistency and
* maintainability of your code.
*/
// Casting to any type is safe because the set will never hold any elements.
@SuppressWarnings({ "unchecked" })
public static <E> ImmutableSet<E> of() {
return (ImmutableSet<E>) EmptyImmutableSet.INSTANCE;
}
/**
* Returns an immutable set containing a single element. This set behaves and
* performs comparably to {@link Collections#singleton}, 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 element) {
return new SingletonImmutableSet<E>(element);
}
/**
* Returns an immutable set containing the given elements, in order. Repeated
* occurrences of an element (according to {@link Object#equals}) after the
* first are ignored.
*
* @throws NullPointerException if any element is null
*/
public static <E> ImmutableSet<E> of(E e1, E e2) {
return construct(2, e1, e2);
}
/**
* Returns an immutable set containing the given elements, in order. Repeated
* occurrences of an element (according to {@link Object#equals}) after the
* first are ignored.
*
* @throws NullPointerException if any element is null
*/
public static <E> ImmutableSet<E> of(E e1, E e2, E e3) {
return construct(3, e1, e2, e3);
}
/**
* Returns an immutable set containing the given elements, in order. Repeated
* occurrences of an element (according to {@link Object#equals}) after the
* first are ignored.
*
* @throws NullPointerException if any element is null
*/
public static <E> ImmutableSet<E> of(E e1, E e2, E e3, E e4) {
return construct(4, e1, e2, e3, e4);
}
/**
* Returns an immutable set containing the given elements, in order. Repeated
* occurrences of an element (according to {@link Object#equals}) after the
* first are ignored.
*
* @throws NullPointerException if any element is null
*/
public static <E> ImmutableSet<E> of(E e1, E e2, E e3, E e4, E e5) {
return construct(5, e1, e2, e3, e4, e5);
}
/**
* Returns an immutable set containing the given elements, in order. Repeated
* occurrences of an element (according to {@link Object#equals}) after the
* first are ignored.
*
* @throws NullPointerException if any element is null
* @since 3.0 (source-compatible since 2.0)
*/
public static <E> ImmutableSet<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E... others) {
final int paramCount = 6;
Object[] elements = new Object[paramCount + others.length];
elements[0] = e1;
elements[1] = e2;
elements[2] = e3;
elements[3] = e4;
elements[4] = e5;
elements[5] = e6;
System.arraycopy(others, 0, elements, paramCount, others.length);
return construct(elements.length, elements);
}
/**
* Constructs an {@code ImmutableSet} from the first {@code n} elements of the
* specified array. If {@code k} is the size of the returned
* {@code ImmutableSet}, then the unique elements of {@code elements} will be in
* the first {@code k} positions, and {@code elements[i] == null} for
* {@code k <= i < n}.
*
* <p>
* This may modify {@code elements}. Additionally, if
* {@code n == elements.length} and {@code elements} contains no duplicates,
* {@code elements} may be used without copying in the returned
* {@code ImmutableSet}, in which case it may no longer be modified.
*
* <p>
* {@code elements} may contain only values of type {@code E}.
*
* @throws NullPointerException if any of the first {@code n} elements of
* {@code elements} is null
*/
private static <E> ImmutableSet<E> construct(int n, Object... elements) {
switch (n) {
case 0:
return of();
case 1:
@SuppressWarnings("unchecked") // safe; elements contains only E's
E elem = (E) elements[0];
return of(elem);
default:
// continue below to handle the general case
}
int tableSize = chooseTableSize(n);
Object[] table = new Object[tableSize];
int mask = tableSize - 1;
int hashCode = 0;
int uniques = 0;
for (int i = 0; i < n; i++) {
Object element = checkElementNotNull(elements[i], i);
int hash = element.hashCode();
for (int j = Hashing.smear(hash);; j++) {
int index = j & mask;
Object value = table[index];
if (value == null) {
// Came to an empty slot. Put the element here.
elements[uniques++] = element;
table[index] = element;
hashCode += hash;
break;
} else if (value.equals(element)) {
break;
}
}
}
Arrays.fill(elements, uniques, n, null);
if (uniques == 1) {
// There is only one element or elements are all duplicates
@SuppressWarnings("unchecked") // we are careful to only pass in E
E element = (E) elements[0];
return new SingletonImmutableSet<E>(element, hashCode);
} else if (tableSize != chooseTableSize(uniques)) {
// Resize the table when the array includes too many duplicates.
// when this happens, we have already made a copy
return construct(uniques, elements);
} else {
Object[] uniqueElements = (uniques < elements.length) ? ObjectArrays.arraysCopyOf(elements, uniques)
: elements;
return new RegularImmutableSet<E>(uniqueElements, hashCode, table, mask);
}
}
// We use power-of-2 tables, and this is the highest int that's a power of 2
static final int MAX_TABLE_SIZE = Ints.MAX_POWER_OF_TWO;
// Represents how tightly we can pack things, as a maximum.
private static final double DESIRED_LOAD_FACTOR = 0.7;
// If the set has this many elements, it will "max out" the table size
private static final int CUTOFF = (int) (MAX_TABLE_SIZE * DESIRED_LOAD_FACTOR);
/**
* 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.
*
* <p>
* Do not call this method with setSize < 2.
*/
@VisibleForTesting
static int chooseTableSize(int setSize) {
// Correct the size for open addressing to match desired load factor.
if (setSize < CUTOFF) {
// Round up to the next highest power of 2.
int tableSize = Integer.highestOneBit(setSize - 1) << 1;
while (tableSize * DESIRED_LOAD_FACTOR < setSize) {
tableSize <<= 1;
}
return tableSize;
}
// The table can't be completely full or we'll get infinite reprobes
checkArgument(setSize < MAX_TABLE_SIZE, "collection too large");
return MAX_TABLE_SIZE;
}
/**
* Returns an immutable set containing the given elements, in order. Repeated
* occurrences of an element (according to {@link Object#equals}) after the
* first are ignored.
*
* @throws NullPointerException if any of {@code elements} is null
* @since 3.0
*/
public static <E> ImmutableSet<E> copyOf(E[] elements) {
switch (elements.length) {
case 0:
return of();
case 1:
return of(elements[0]);
default:
return construct(elements.length, elements.clone());
}
}
/**
* Returns an immutable set containing the given elements, in order. Repeated
* occurrences of an element (according to {@link Object#equals}) after the
* first are ignored. This method iterates over {@code elements} at most once.
*
* <p>
* Note that if {@code s} is a {@code Set<String>}, then {@code
* ImmutableSet.copyOf(s)} returns an {@code ImmutableSet<String>} containing
* each of the strings in {@code s}, while {@code ImmutableSet.of(s)} returns a
* {@code ImmutableSet<Set<String>>} containing one element (the given set
* itself).
*
* <p>
* 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.
*
* @throws NullPointerException if any of {@code elements} is null
*/
public static <E> ImmutableSet<E> copyOf(Iterable<? extends E> elements) {
return (elements instanceof Collection) ? copyOf(Collections2.cast(elements)) : copyOf(elements.iterator());
}
/**
* Returns an immutable set containing the given elements, in order. Repeated
* occurrences of an element (according to {@link Object#equals}) after the
* first are ignored.
*
* @throws NullPointerException if any of {@code elements} is null
*/
public static <E> ImmutableSet<E> copyOf(Iterator<? extends E> elements) {
// We special-case for 0 or 1 elements, but anything further is madness.
if (!elements.hasNext()) {
return of();
}
E first = elements.next();
if (!elements.hasNext()) {
return of(first);
} else {
return new ImmutableSet.Builder<E>().add(first).addAll(elements).build();
}
}
/**
* Returns an immutable set containing the given elements, in order. Repeated
* occurrences of an element (according to {@link Object#equals}) after the
* first are ignored. This method iterates over {@code elements} at most once.
*
* <p>
* Note that if {@code s} is a {@code Set<String>}, then {@code
* ImmutableSet.copyOf(s)} returns an {@code ImmutableSet<String>} containing
* each of the strings in {@code s}, while {@code ImmutableSet.of(s)} returns a
* {@code ImmutableSet<Set<String>>} containing one element (the given set
* itself).
*
* <p>
* <b>Note:</b> Despite what the method name suggests, {@code 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 {@code 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:
* <ul>
* <li>A full copy will be done of any {@code ImmutableSortedSet}.</li>
* <li>{@code ImmutableSet.copyOf()} is idempotent with respect to pointer
* equality.</li>
* </ul>
*
* <p>
* This method is safe to use even when {@code elements} is a synchronized or
* concurrent collection that is currently being modified by another thread.
*
* @throws NullPointerException if any of {@code elements} is null
* @since 7.0 (source-compatible since 2.0)
*/
public static <E> ImmutableSet<E> copyOf(Collection<? extends E> elements) {
/*
* TODO(user): consider checking for ImmutableAsList here TODO(user): consider
* checking for Multiset here
*/
if (elements instanceof ImmutableSet && !(elements instanceof ImmutableSortedSet)) {
@SuppressWarnings("unchecked") // all supported methods are covariant
ImmutableSet<E> set = (ImmutableSet<E>) elements;
if (!set.isPartialView()) {
return set;
}
} else if (elements instanceof EnumSet) {
return copyOfEnumSet((EnumSet) elements);
}
Object[] array = elements.toArray();
return construct(array.length, array);
}
private static <E extends Enum<E>> ImmutableSet<E> copyOfEnumSet(EnumSet<E> enumSet) {
return ImmutableEnumSet.asImmutable(EnumSet.copyOf(enumSet));
}
ImmutableSet() {
}
/** Returns {@code true} if the {@code hashCode()} method runs quickly. */
boolean isHashCodeFast() {
return false;
}
@Override
public boolean equals(@Nullable Object object) {
if (object == this) {
return true;
} else if (object instanceof ImmutableSet && isHashCodeFast() && ((ImmutableSet<?>) object).isHashCodeFast()
&& hashCode() != object.hashCode()) {
return false;
}
return Sets.equalsImpl(this, object);
}
@Override
public int hashCode() {
return Sets.hashCodeImpl(this);
}
// This declaration is needed to make Set.iterator() and
// ImmutableCollection.iterator() consistent.
@Override
public abstract UnmodifiableIterator<E> iterator();
/*
* This class is used to serialize all ImmutableSet instances, except for
* ImmutableEnumSet/ImmutableSortedSet, regardless of implementation type. It
* captures their "logical contents" and they are reconstructed using public
* static factories. This is necessary to ensure that the existence of a
* particular implementation type is an implementation detail.
*/
private static class SerializedForm implements Serializable {
final Object[] elements;
SerializedForm(Object[] elements) {
this.elements = elements;
}
Object readResolve() {
return copyOf(elements);
}
private static final long serialVersionUID = 0;
}
@Override
Object writeReplace() {
return new SerializedForm(toArray());
}
/**
* Returns a new builder. The generated builder is equivalent to the builder
* created by the {@link Builder} constructor.
*/
public static <E> Builder<E> builder() {
return new Builder<E>();
}
/**
* A builder for creating immutable set instances, especially {@code public
* static final} sets ("constant sets"). Example:
*
* <pre>
* {
* &#64;code
*
* public static final ImmutableSet<Color> GOOGLE_COLORS = new ImmutableSet.Builder<Color>()
* .addAll(WEBSAFE_COLORS).add(new Color(0, 191, 255)).build();
* }
* </pre>
*
* <p>
* Builder instances can be reused; it is safe to call {@link #build} multiple
* times to build multiple sets in series. Each set is a superset of the set
* created before it.
*
* @since 2.0 (imported from Google Collections Library)
*/
public static class Builder<E> extends ImmutableCollection.ArrayBasedBuilder<E> {
/**
* Creates a new builder. The returned builder is equivalent to the builder
* generated by {@link ImmutableSet#builder}.
*/
public Builder() {
this(DEFAULT_INITIAL_CAPACITY);
}
Builder(int capacity) {
super(capacity);
}
/**
* Adds {@code element} to the {@code ImmutableSet}. If the {@code
* ImmutableSet} already contains {@code element}, then {@code add} has no
* effect (only the previously added element is retained).
*
* @param element the element to add
* @return this {@code Builder} object
* @throws NullPointerException if {@code element} is null
*/
@Override
public Builder<E> add(E element) {
super.add(element);
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableSet}, ignoring
* duplicate elements (only the first duplicate element is added).
*
* @param elements the elements to add
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a null
* element
*/
@Override
public Builder<E> add(E... elements) {
super.add(elements);
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableSet}, ignoring
* duplicate elements (only the first duplicate element is added).
*
* @param elements the {@code Iterable} to add to the {@code ImmutableSet}
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a null
* element
*/
@Override
public Builder<E> addAll(Iterable<? extends E> elements) {
super.addAll(elements);
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableSet}, ignoring
* duplicate elements (only the first duplicate element is added).
*
* @param elements the elements to add to the {@code ImmutableSet}
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a null
* element
*/
@Override
public Builder<E> addAll(Iterator<? extends E> elements) {
super.addAll(elements);
return this;
}
/**
* Returns a newly-created {@code ImmutableSet} based on the contents of the
* {@code Builder}.
*/
@Override
public ImmutableSet<E> build() {
ImmutableSet<E> result = construct(size, contents);
// construct has the side effect of deduping contents, so we update size
// accordingly.
size = result.size();
return result;
}
}
}