com.google.common.collect.ImmutableList Maven / Gradle / Ivy
/*
* 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.checkElementIndex;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkPositionIndex;
import static com.google.common.base.Preconditions.checkPositionIndexes;
import static com.google.common.collect.ObjectArrays.checkElementNotNull;
import com.google.common.annotations.GwtCompatible;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.RandomAccess;
import javax.annotation.Nullable;
/**
* A high-performance, immutable, random-access {@code List} implementation.
* Does not permit null elements.
*
* Unlike {@link Collections#unmodifiableList}, which is a view of a
* separate collection that can still change, an instance of {@code
* ImmutableList} contains its own private data and will never change.
* {@code ImmutableList} is convenient for {@code public static final} lists
* ("constant lists") and also lets you easily make a "defensive copy" of a list
* provided to your class by a caller.
*
*
Note: Although this class is not final, it cannot be subclassed as
* it has no public or protected constructors. Thus, instances of this type are
* guaranteed to be immutable.
*
*
See the Guava User Guide article on
* immutable collections.
*
* @see ImmutableMap
* @see ImmutableSet
* @author Kevin Bourrillion
* @since 2.0 (imported from Google Collections Library)
*/
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableList extends ImmutableCollection
implements List, RandomAccess {
/**
* Returns the empty immutable list. This set behaves and performs comparably
* to {@link Collections#emptyList}, and is preferable mainly for consistency
* and maintainability of your code.
*/
// Casting to any type is safe because the list will never hold any elements.
@SuppressWarnings("unchecked")
public static ImmutableList of() {
return (ImmutableList) EmptyImmutableList.INSTANCE;
}
/**
* Returns an immutable list containing a single element. This list 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.
*
* @throws NullPointerException if {@code element} is null
*/
public static ImmutableList of(E element) {
return new SingletonImmutableList(element);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(E e1, E e2) {
return construct(e1, e2);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(E e1, E e2, E e3) {
return construct(e1, e2, e3);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(E e1, E e2, E e3, E e4) {
return construct(e1, e2, e3, e4);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(E e1, E e2, E e3, E e4, E e5) {
return construct(e1, e2, e3, e4, e5);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(E e1, E e2, E e3, E e4, E e5, E e6) {
return construct(e1, e2, e3, e4, e5, e6);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(
E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
return construct(e1, e2, e3, e4, e5, e6, e7);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(
E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
return construct(e1, e2, e3, e4, e5, e6, e7, e8);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(
E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
return construct(e1, e2, e3, e4, e5, e6, e7, e8, e9);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(
E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) {
return construct(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(
E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10, E e11) {
return construct(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11);
}
// These go up to eleven. After that, you just get the varargs form, and
// whatever warnings might come along with it. :(
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
* @since 3.0 (source-compatible since 2.0)
*/
public static ImmutableList of(
E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10, E e11, E e12,
E... others) {
Object[] array = new Object[12 + others.length];
array[0] = e1;
array[1] = e2;
array[2] = e3;
array[3] = e4;
array[4] = e5;
array[5] = e6;
array[6] = e7;
array[7] = e8;
array[8] = e9;
array[9] = e10;
array[10] = e11;
array[11] = e12;
System.arraycopy(others, 0, array, 12, others.length);
return construct(array);
}
/**
* Returns an immutable list containing the given elements, in order. If
* {@code elements} is a {@link Collection}, this method behaves exactly as
* {@link #copyOf(Collection)}; otherwise, it behaves exactly as {@code
* copyOf(elements.iterator()}.
*
* @throws NullPointerException if any of {@code elements} is null
*/
public static ImmutableList copyOf(Iterable elements) {
checkNotNull(elements); // TODO(kevinb): is this here only for GWT?
return (elements instanceof Collection)
? copyOf(Collections2.cast(elements))
: copyOf(elements.iterator());
}
/**
* Returns an immutable list containing the given elements, in order.
*
* 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.
*
*
Note that if {@code list} is a {@code List}, then {@code
* ImmutableList.copyOf(list)} returns an {@code ImmutableList}
* containing each of the strings in {@code list}, while
* ImmutableList.of(list)} returns an {@code ImmutableList>}
* containing one element (the given list itself).
*
* 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
*/
public static ImmutableList copyOf(Collection elements) {
if (elements instanceof ImmutableCollection) {
@SuppressWarnings("unchecked") // all supported methods are covariant
ImmutableList list = ((ImmutableCollection) elements).asList();
return list.isPartialView() ? copyFromCollection(list) : list;
}
return copyFromCollection(elements);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any of {@code elements} is null
*/
public static ImmutableList copyOf(Iterator elements) {
// We special-case for 0 or 1 elements, but going further is madness.
if (!elements.hasNext()) {
return of();
}
E first = elements.next();
if (!elements.hasNext()) {
return of(first);
} else {
return new ImmutableList.Builder()
.add(first)
.addAll(elements)
.build();
}
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any of {@code elements} is null
* @since 3.0
*/
public static ImmutableList copyOf(E[] elements) {
switch (elements.length) {
case 0:
return ImmutableList.of();
case 1:
return new SingletonImmutableList(elements[0]);
default:
return construct(elements.clone());
}
}
/**
* Views the array as an immutable list. The array must have only non-null {@code E} elements.
*
* The array must be internally created.
*/
static ImmutableList asImmutableList(Object[] elements) {
switch (elements.length) {
case 0:
return of();
case 1:
@SuppressWarnings("unchecked") // collection had only Es in it
ImmutableList list = new SingletonImmutableList((E) elements[0]);
return list;
default:
return construct(elements);
}
}
private static ImmutableList copyFromCollection(
Collection collection) {
return asImmutableList(collection.toArray());
}
/** {@code elements} has to be internally created array. */
private static ImmutableList construct(Object... elements) {
for (int i = 0; i < elements.length; i++) {
ObjectArrays.checkElementNotNull(elements[i], i);
}
return new RegularImmutableList(elements);
}
ImmutableList() {}
// This declaration is needed to make List.iterator() and
// ImmutableCollection.iterator() consistent.
@Override public UnmodifiableIterator iterator() {
return listIterator();
}
@Override public UnmodifiableListIterator listIterator() {
return listIterator(0);
}
@Override public UnmodifiableListIterator listIterator(int index) {
return new AbstractIndexedListIterator(size(), index) {
@Override
protected E get(int index) {
return ImmutableList.this.get(index);
}
};
}
@Override
public int indexOf(@Nullable Object object) {
return (object == null) ? -1 : Lists.indexOfImpl(this, object);
}
@Override
public int lastIndexOf(@Nullable Object object) {
return (object == null) ? -1 : Lists.lastIndexOfImpl(this, object);
}
@Override
public boolean contains(@Nullable Object object) {
return indexOf(object) >= 0;
}
// constrain the return type to ImmutableList
/**
* Returns an immutable list of the elements between the specified {@code
* fromIndex}, inclusive, and {@code toIndex}, exclusive. (If {@code
* fromIndex} and {@code toIndex} are equal, the empty immutable list is
* returned.)
*/
@Override
public ImmutableList subList(int fromIndex, int toIndex) {
checkPositionIndexes(fromIndex, toIndex, size());
int length = toIndex - fromIndex;
switch (length) {
case 0:
return of();
case 1:
return of(get(fromIndex));
default:
return subListUnchecked(fromIndex, toIndex);
}
}
/**
* Called by the default implementation of {@link #subList} when {@code
* toIndex - fromIndex > 1}, after index validation has already been
* performed.
*/
ImmutableList subListUnchecked(int fromIndex, int toIndex) {
return new SubList(fromIndex, toIndex - fromIndex);
}
class SubList extends ImmutableList {
transient final int offset;
transient final int length;
SubList(int offset, int length) {
this.offset = offset;
this.length = length;
}
@Override
public int size() {
return length;
}
@Override
public E get(int index) {
checkElementIndex(index, length);
return ImmutableList.this.get(index + offset);
}
@Override
public ImmutableList subList(int fromIndex, int toIndex) {
checkPositionIndexes(fromIndex, toIndex, length);
return ImmutableList.this.subList(fromIndex + offset, toIndex + offset);
}
@Override
boolean isPartialView() {
return true;
}
}
/**
* Guaranteed to throw an exception and leave the list unmodified.
*
* @throws UnsupportedOperationException always
*/
@Override
public final boolean addAll(int index, Collection newElements) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the list unmodified.
*
* @throws UnsupportedOperationException always
*/
@Override
public final E set(int index, E element) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the list unmodified.
*
* @throws UnsupportedOperationException always
*/
@Override
public final void add(int index, E element) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the list unmodified.
*
* @throws UnsupportedOperationException always
*/
@Override
public final E remove(int index) {
throw new UnsupportedOperationException();
}
/**
* Returns this list instance.
*
* @since 2.0
*/
@Override public ImmutableList asList() {
return this;
}
/**
* Returns a view of this immutable list in reverse order. For example, {@code
* ImmutableList.of(1, 2, 3).reverse()} is equivalent to {@code
* ImmutableList.of(3, 2, 1)}.
*
* @return a view of this immutable list in reverse order
* @since 7.0
*/
public ImmutableList reverse() {
return new ReverseImmutableList(this);
}
private static class ReverseImmutableList extends ImmutableList {
private final transient ImmutableList forwardList;
private final transient int size;
ReverseImmutableList(ImmutableList backingList) {
this.forwardList = backingList;
this.size = backingList.size();
}
private int reverseIndex(int index) {
return (size - 1) - index;
}
private int reversePosition(int index) {
return size - index;
}
@Override public ImmutableList reverse() {
return forwardList;
}
@Override public boolean contains(@Nullable Object object) {
return forwardList.contains(object);
}
@Override public boolean containsAll(Collection targets) {
return forwardList.containsAll(targets);
}
@Override public int indexOf(@Nullable Object object) {
int index = forwardList.lastIndexOf(object);
return (index >= 0) ? reverseIndex(index) : -1;
}
@Override public int lastIndexOf(@Nullable Object object) {
int index = forwardList.indexOf(object);
return (index >= 0) ? reverseIndex(index) : -1;
}
@Override public ImmutableList subList(int fromIndex, int toIndex) {
checkPositionIndexes(fromIndex, toIndex, size);
return forwardList.subList(
reversePosition(toIndex), reversePosition(fromIndex)).reverse();
}
@Override public E get(int index) {
checkElementIndex(index, size);
return forwardList.get(reverseIndex(index));
}
@Override public UnmodifiableListIterator listIterator(int index) {
checkPositionIndex(index, size);
final UnmodifiableListIterator forward =
forwardList.listIterator(reversePosition(index));
return new UnmodifiableListIterator() {
@Override public boolean hasNext() {
return forward.hasPrevious();
}
@Override public boolean hasPrevious() {
return forward.hasNext();
}
@Override public E next() {
return forward.previous();
}
@Override public int nextIndex() {
return reverseIndex(forward.previousIndex());
}
@Override public E previous() {
return forward.next();
}
@Override public int previousIndex() {
return reverseIndex(forward.nextIndex());
}
};
}
@Override public int size() {
return size;
}
@Override public boolean isEmpty() {
return forwardList.isEmpty();
}
@Override boolean isPartialView() {
return forwardList.isPartialView();
}
}
@Override public boolean equals(Object obj) {
return Lists.equalsImpl(this, obj);
}
@Override public int hashCode() {
return Lists.hashCodeImpl(this);
}
/*
* Serializes ImmutableLists as their logical contents. This ensures that
* implementation types do not leak into the serialized representation.
*/
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;
}
private void readObject(ObjectInputStream stream)
throws InvalidObjectException {
throw new InvalidObjectException("Use SerializedForm");
}
@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 Builder builder() {
return new Builder();
}
/**
* A builder for creating immutable list instances, especially {@code public
* static final} lists ("constant lists"). Example: {@code
*
* public static final ImmutableList GOOGLE_COLORS
* = new ImmutableList.Builder()
* .addAll(WEBSAFE_COLORS)
* .add(new Color(0, 191, 255))
* .build();}
*
* Builder instances can be reused; it is safe to call {@link #build} multiple
* times to build multiple lists in series. Each new list contains all the
* elements of the ones created before it.
*
* @since 2.0 (imported from Google Collections Library)
*/
public static final class Builder extends ImmutableCollection.Builder {
private Object[] contents;
private int size;
/**
* Creates a new builder. The returned builder is equivalent to the builder
* generated by {@link ImmutableList#builder}.
*/
public Builder() {
this(DEFAULT_INITIAL_CAPACITY);
}
// TODO(user): consider exposing this
Builder(int capacity) {
this.contents = new Object[capacity];
this.size = 0;
}
/**
* Expand capacity to allow the specified number of elements to be added.
*/
Builder expandFor(int count) {
int minCapacity = size + count;
if (contents.length < minCapacity) {
this.contents = ObjectArrays.arraysCopyOf(
this.contents, expandedCapacity(contents.length, minCapacity));
}
return this;
}
/**
* Adds {@code element} to the {@code ImmutableList}.
*
* @param element the element to add
* @return this {@code Builder} object
* @throws NullPointerException if {@code element} is null
*/
@Override public Builder add(E element) {
checkNotNull(element);
expandFor(1);
contents[size++] = element;
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableList}.
*
* @param elements the {@code Iterable} to add to the {@code ImmutableList}
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a
* null element
*/
@Override public Builder addAll(Iterable elements) {
if (elements instanceof Collection) {
Collection collection = (Collection) elements;
expandFor(collection.size());
}
super.addAll(elements);
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableList}.
*
* @param elements the {@code Iterable} to add to the {@code ImmutableList}
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a
* null element
*/
@Override public Builder add(E... elements) {
for (int i = 0; i < elements.length; i++) {
checkElementNotNull(elements[i], i);
}
expandFor(elements.length);
System.arraycopy(elements, 0, contents, size, elements.length);
size += elements.length;
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableList}.
*
* @param elements the {@code Iterable} to add to the {@code ImmutableList}
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a
* null element
*/
@Override public Builder addAll(Iterator elements) {
super.addAll(elements);
return this;
}
/**
* Returns a newly-created {@code ImmutableList} based on the contents of
* the {@code Builder}.
*/
@Override public ImmutableList build() {
switch (size) {
case 0:
return of();
case 1:
@SuppressWarnings("unchecked") // guaranteed to be an E
E singleElement = (E) contents[0];
return of(singleElement);
default:
if (size == contents.length) {
// no need to copy; any further add operations on the builder will copy the buffer
return new RegularImmutableList(contents);
} else {
return new RegularImmutableList(ObjectArrays.arraysCopyOf(contents, size));
}
}
}
}
}