| /* |
| * Copyright (C) 2008 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.checkNotNull; |
| import static com.google.common.collect.CollectPreconditions.checkNonnegative; |
| import static com.google.common.collect.ObjectArrays.checkElementsNotNull; |
| |
| import com.google.common.annotations.GwtCompatible; |
| import com.google.errorprone.annotations.CanIgnoreReturnValue; |
| import java.io.Serializable; |
| import java.util.AbstractCollection; |
| import java.util.Arrays; |
| import java.util.Collection; |
| import java.util.Collections; |
| import java.util.Iterator; |
| import java.util.List; |
| import org.checkerframework.checker.nullness.compatqual.NullableDecl; |
| |
| /** |
| * A {@link Collection} whose contents will never change, and which offers a few additional |
| * guarantees detailed below. |
| * |
| * <p><b>Warning:</b> avoid <i>direct</i> usage of {@link ImmutableCollection} as a type (just as |
| * with {@link Collection} itself). Prefer subtypes such as {@link ImmutableSet} or {@link |
| * ImmutableList}, which have well-defined {@link #equals} semantics, thus avoiding a common source |
| * of bugs and confusion. |
| * |
| * <h3>About <i>all</i> {@code Immutable-} collections</h3> |
| * |
| * <p>The remainder of this documentation applies to every public {@code Immutable-} type in this |
| * package, whether it is a subtype of {@code ImmutableCollection} or not. |
| * |
| * <h4>Guarantees</h4> |
| * |
| * <p>Each makes the following guarantees: |
| * |
| * <ul> |
| * <li><b>Shallow immutability.</b> Elements can never be added, removed or replaced in this |
| * collection. This is a stronger guarantee than that of {@link |
| * Collections#unmodifiableCollection}, whose contents change whenever the wrapped collection |
| * is modified. |
| * <li><b>Null-hostility.</b> This collection will never contain a null element. |
| * <li><b>Deterministic iteration.</b> The iteration order is always well-defined, depending on |
| * how the collection was created. Typically this is insertion order unless an explicit |
| * ordering is otherwise specified (e.g. {@link ImmutableSortedSet#naturalOrder}). See the |
| * appropriate factory method for details. View collections such as {@link |
| * ImmutableMultiset#elementSet} iterate in the same order as the parent, except as noted. |
| * <li><b>Thread safety.</b> It is safe to access this collection concurrently from multiple |
| * threads. |
| * <li><b>Integrity.</b> This type cannot be subclassed outside this package (which would allow |
| * these guarantees to be violated). |
| * </ul> |
| * |
| * <h4>"Interfaces", not implementations</h4> |
| * |
| * <p>These are classes instead of interfaces to prevent external subtyping, but should be thought |
| * of as interfaces in every important sense. Each public class such as {@link ImmutableSet} is a |
| * <i>type</i> offering meaningful behavioral guarantees. This is substantially different from the |
| * case of (say) {@link HashSet}, which is an <i>implementation</i>, with semantics that were |
| * largely defined by its supertype. |
| * |
| * <p>For field types and method return types, you should generally use the immutable type (such as |
| * {@link ImmutableList}) instead of the general collection interface type (such as {@link List}). |
| * This communicates to your callers all of the semantic guarantees listed above, which is almost |
| * always very useful information. |
| * |
| * <p>On the other hand, a <i>parameter</i> type of {@link ImmutableList} is generally a nuisance to |
| * callers. Instead, accept {@link Iterable} and have your method or constructor body pass it to the |
| * appropriate {@code copyOf} method itself. |
| * |
| * <p>Expressing the immutability guarantee directly in the type that user code references is a |
| * powerful advantage. Although Java offers certain immutable collection factory methods, such as |
| * {@link Collections#singleton(Object)} and <a |
| * href="https://docs.oracle.com/javase/9/docs/api/java/util/Set.html#immutable">{@code Set.of}</a>, |
| * we recommend using <i>these</i> classes instead for this reason (as well as for consistency). |
| * |
| * <h4>Creation</h4> |
| * |
| * <p>Except for logically "abstract" types like {@code ImmutableCollection} itself, each {@code |
| * Immutable} type provides the static operations you need to obtain instances of that type. These |
| * usually include: |
| * |
| * <ul> |
| * <li>Static methods named {@code of}, accepting an explicit list of elements or entries. |
| * <li>Static methods named {@code copyOf} (or {@code copyOfSorted}), accepting an existing |
| * collection whose contents should be copied. |
| * <li>A static nested {@code Builder} class which can be used to populate a new immutable |
| * instance. |
| * </ul> |
| * |
| * <h4>Warnings</h4> |
| * |
| * <ul> |
| * <li><b>Warning:</b> as with any collection, it is almost always a bad idea to modify an element |
| * (in a way that affects its {@link Object#equals} behavior) while it is contained in a |
| * collection. Undefined behavior and bugs will result. It's generally best to avoid using |
| * mutable objects as elements at all, as many users may expect your "immutable" object to be |
| * <i>deeply</i> immutable. |
| * </ul> |
| * |
| * <h4>Performance notes</h4> |
| * |
| * <ul> |
| * <li>Implementations can be generally assumed to prioritize memory efficiency, then speed of |
| * access, and lastly speed of creation. |
| * <li>The {@code copyOf} methods will sometimes recognize that the actual copy operation is |
| * unnecessary; for example, {@code 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. |
| * <li><b>Warning:</b> a view collection such as {@link ImmutableMap#keySet} or {@link |
| * ImmutableList#subList} may retain a reference to the entire data set, preventing it from |
| * being garbage collected. If some of the data is no longer reachable through other means, |
| * this constitutes a memory leak. Pass the view collection to the appropriate {@code copyOf} |
| * method to obtain a correctly-sized copy. |
| * <li>The performance of using the associated {@code Builder} class can be assumed to be no |
| * worse, and possibly better, than creating a mutable collection and copying it. |
| * <li>Implementations generally do not cache hash codes. If your element or key type has a slow |
| * {@code hashCode} implementation, it should cache it itself. |
| * </ul> |
| * |
| * <h4>Example usage</h4> |
| * |
| * <pre>{@code |
| * class Foo { |
| * private static final ImmutableSet<String> RESERVED_CODES = |
| * ImmutableSet.of("AZ", "CQ", "ZX"); |
| * |
| * private final ImmutableSet<String> codes; |
| * |
| * public Foo(Iterable<String> codes) { |
| * this.codes = ImmutableSet.copyOf(codes); |
| * checkArgument(Collections.disjoint(this.codes, RESERVED_CODES)); |
| * } |
| * } |
| * }</pre> |
| * |
| * <h3>See also</h3> |
| * |
| * <p>See the Guava User Guide article on <a href= |
| * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained"> immutable collections</a>. |
| * |
| * @since 2.0 |
| */ |
| @GwtCompatible(emulated = true) |
| @SuppressWarnings("serial") // we're overriding default serialization |
| // TODO(kevinb): I think we should push everything down to "BaseImmutableCollection" or something, |
| // just to do everything we can to emphasize the "practically an interface" nature of this class. |
| public abstract class ImmutableCollection<E> extends AbstractCollection<E> implements Serializable { |
| |
| ImmutableCollection() {} |
| |
| /** Returns an unmodifiable iterator across the elements in this collection. */ |
| @Override |
| public abstract UnmodifiableIterator<E> iterator(); |
| |
| private static final Object[] EMPTY_ARRAY = {}; |
| |
| @Override |
| public final Object[] toArray() { |
| return toArray(EMPTY_ARRAY); |
| } |
| |
| @CanIgnoreReturnValue |
| @Override |
| public final <T> T[] toArray(T[] other) { |
| checkNotNull(other); |
| int size = size(); |
| |
| if (other.length < size) { |
| Object[] internal = internalArray(); |
| if (internal != null) { |
| return Platform.copy(internal, internalArrayStart(), internalArrayEnd(), other); |
| } |
| other = ObjectArrays.newArray(other, size); |
| } else if (other.length > size) { |
| other[size] = null; |
| } |
| copyIntoArray(other, 0); |
| return other; |
| } |
| |
| /** If this collection is backed by an array of its elements in insertion order, returns it. */ |
| Object[] internalArray() { |
| return null; |
| } |
| |
| /** |
| * If this collection is backed by an array of its elements in insertion order, returns the offset |
| * where this collection's elements start. |
| */ |
| int internalArrayStart() { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * If this collection is backed by an array of its elements in insertion order, returns the offset |
| * where this collection's elements end. |
| */ |
| int internalArrayEnd() { |
| throw new UnsupportedOperationException(); |
| } |
| |
| @Override |
| public abstract boolean contains(@NullableDecl Object object); |
| |
| /** |
| * Guaranteed to throw an exception and leave the collection unmodified. |
| * |
| * @throws UnsupportedOperationException always |
| * @deprecated Unsupported operation. |
| */ |
| @CanIgnoreReturnValue |
| @Deprecated |
| @Override |
| public final boolean add(E e) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * Guaranteed to throw an exception and leave the collection unmodified. |
| * |
| * @throws UnsupportedOperationException always |
| * @deprecated Unsupported operation. |
| */ |
| @CanIgnoreReturnValue |
| @Deprecated |
| @Override |
| public final boolean remove(Object object) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * Guaranteed to throw an exception and leave the collection unmodified. |
| * |
| * @throws UnsupportedOperationException always |
| * @deprecated Unsupported operation. |
| */ |
| @CanIgnoreReturnValue |
| @Deprecated |
| @Override |
| public final boolean addAll(Collection<? extends E> newElements) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * Guaranteed to throw an exception and leave the collection unmodified. |
| * |
| * @throws UnsupportedOperationException always |
| * @deprecated Unsupported operation. |
| */ |
| @CanIgnoreReturnValue |
| @Deprecated |
| @Override |
| public final boolean removeAll(Collection<?> oldElements) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * Guaranteed to throw an exception and leave the collection unmodified. |
| * |
| * @throws UnsupportedOperationException always |
| * @deprecated Unsupported operation. |
| */ |
| @CanIgnoreReturnValue |
| @Deprecated |
| @Override |
| public final boolean retainAll(Collection<?> elementsToKeep) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * Guaranteed to throw an exception and leave the collection unmodified. |
| * |
| * @throws UnsupportedOperationException always |
| * @deprecated Unsupported operation. |
| */ |
| @Deprecated |
| @Override |
| public final void clear() { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * Returns an {@code ImmutableList} containing the same elements, in the same order, as this |
| * collection. |
| * |
| * <p><b>Performance note:</b> 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. |
| * |
| * @since 2.0 |
| */ |
| public ImmutableList<E> asList() { |
| return isEmpty() ? ImmutableList.<E>of() : ImmutableList.<E>asImmutableList(toArray()); |
| } |
| |
| /** |
| * Returns {@code true} if this immutable collection's implementation contains references to |
| * user-created objects that aren't accessible via this collection's methods. This is generally |
| * used to determine whether {@code copyOf} implementations should make an explicit copy to avoid |
| * memory leaks. |
| */ |
| abstract boolean isPartialView(); |
| |
| /** |
| * Copies the contents of this immutable collection into the specified array at the specified |
| * offset. Returns {@code offset + size()}. |
| */ |
| @CanIgnoreReturnValue |
| int copyIntoArray(Object[] dst, int offset) { |
| for (E e : this) { |
| dst[offset++] = e; |
| } |
| return offset; |
| } |
| |
| Object writeReplace() { |
| // We serialize by default to ImmutableList, the simplest thing that works. |
| return new ImmutableList.SerializedForm(toArray()); |
| } |
| |
| /** |
| * Abstract base class for builders of {@link ImmutableCollection} types. |
| * |
| * @since 10.0 |
| */ |
| public abstract static class Builder<E> { |
| static final int DEFAULT_INITIAL_CAPACITY = 4; |
| |
| static int expandedCapacity(int oldCapacity, int minCapacity) { |
| if (minCapacity < 0) { |
| throw new AssertionError("cannot store more than MAX_VALUE elements"); |
| } |
| // careful of overflow! |
| int newCapacity = oldCapacity + (oldCapacity >> 1) + 1; |
| if (newCapacity < minCapacity) { |
| newCapacity = Integer.highestOneBit(minCapacity - 1) << 1; |
| } |
| if (newCapacity < 0) { |
| newCapacity = Integer.MAX_VALUE; |
| // guaranteed to be >= newCapacity |
| } |
| return newCapacity; |
| } |
| |
| Builder() {} |
| |
| /** |
| * Adds {@code element} to the {@code ImmutableCollection} being built. |
| * |
| * <p>Note that each builder class covariantly returns its own type from this method. |
| * |
| * @param element the element to add |
| * @return this {@code Builder} instance |
| * @throws NullPointerException if {@code element} is null |
| */ |
| @CanIgnoreReturnValue |
| public abstract Builder<E> add(E element); |
| |
| /** |
| * Adds each element of {@code elements} to the {@code ImmutableCollection} being built. |
| * |
| * <p>Note that each builder class overrides this method in order to covariantly return its own |
| * type. |
| * |
| * @param elements the elements to add |
| * @return this {@code Builder} instance |
| * @throws NullPointerException if {@code elements} is null or contains a null element |
| */ |
| @CanIgnoreReturnValue |
| public Builder<E> add(E... elements) { |
| for (E element : elements) { |
| add(element); |
| } |
| return this; |
| } |
| |
| /** |
| * Adds each element of {@code elements} to the {@code ImmutableCollection} being built. |
| * |
| * <p>Note that each builder class overrides this method in order to covariantly return its own |
| * type. |
| * |
| * @param elements the elements to add |
| * @return this {@code Builder} instance |
| * @throws NullPointerException if {@code elements} is null or contains a null element |
| */ |
| @CanIgnoreReturnValue |
| public Builder<E> addAll(Iterable<? extends E> elements) { |
| for (E element : elements) { |
| add(element); |
| } |
| return this; |
| } |
| |
| /** |
| * Adds each element of {@code elements} to the {@code ImmutableCollection} being built. |
| * |
| * <p>Note that each builder class overrides this method in order to covariantly return its own |
| * type. |
| * |
| * @param elements the elements to add |
| * @return this {@code Builder} instance |
| * @throws NullPointerException if {@code elements} is null or contains a null element |
| */ |
| @CanIgnoreReturnValue |
| public Builder<E> addAll(Iterator<? extends E> elements) { |
| while (elements.hasNext()) { |
| add(elements.next()); |
| } |
| return this; |
| } |
| |
| /** |
| * Returns a newly-created {@code ImmutableCollection} of the appropriate type, containing the |
| * elements provided to this builder. |
| * |
| * <p>Note that each builder class covariantly returns the appropriate type of {@code |
| * ImmutableCollection} from this method. |
| */ |
| public abstract ImmutableCollection<E> build(); |
| } |
| |
| abstract static class ArrayBasedBuilder<E> extends ImmutableCollection.Builder<E> { |
| Object[] contents; |
| int size; |
| boolean forceCopy; |
| |
| ArrayBasedBuilder(int initialCapacity) { |
| checkNonnegative(initialCapacity, "initialCapacity"); |
| this.contents = new Object[initialCapacity]; |
| this.size = 0; |
| } |
| |
| /* |
| * Expand the absolute capacity of the builder so it can accept at least the specified number of |
| * elements without being resized. Also, if we've already built a collection backed by the |
| * current array, create a new array. |
| */ |
| private void getReadyToExpandTo(int minCapacity) { |
| if (contents.length < minCapacity) { |
| this.contents = |
| Arrays.copyOf(this.contents, expandedCapacity(contents.length, minCapacity)); |
| forceCopy = false; |
| } else if (forceCopy) { |
| this.contents = contents.clone(); |
| forceCopy = false; |
| } |
| } |
| |
| @CanIgnoreReturnValue |
| @Override |
| public ArrayBasedBuilder<E> add(E element) { |
| checkNotNull(element); |
| getReadyToExpandTo(size + 1); |
| contents[size++] = element; |
| return this; |
| } |
| |
| @CanIgnoreReturnValue |
| @Override |
| public Builder<E> add(E... elements) { |
| checkElementsNotNull(elements); |
| getReadyToExpandTo(size + elements.length); |
| System.arraycopy(elements, 0, contents, size, elements.length); |
| size += elements.length; |
| return this; |
| } |
| |
| @CanIgnoreReturnValue |
| @Override |
| public Builder<E> addAll(Iterable<? extends E> elements) { |
| if (elements instanceof Collection) { |
| Collection<?> collection = (Collection<?>) elements; |
| getReadyToExpandTo(size + collection.size()); |
| if (collection instanceof ImmutableCollection) { |
| ImmutableCollection<?> immutableCollection = (ImmutableCollection<?>) collection; |
| size = immutableCollection.copyIntoArray(contents, size); |
| return this; |
| } |
| } |
| super.addAll(elements); |
| return this; |
| } |
| } |
| } |