/*
* 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.checkNotNull;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Preconditions;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.ArrayList;
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.
*
* <p>Unlike {@link Collections#unmodifiableList}, which is a <i>view</i> of a
* separate collection that can still change, an instance of {@code
* ImmutableList} contains its own private data and will <i>never</i> 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.
*
* <p><b>Note:</b> 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 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<E> extends ImmutableCollection<E>
implements List<E>, 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 <E> ImmutableList<E> of() {
return (ImmutableList<E>) 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 <E> ImmutableList<E> of(E element) {
return new SingletonImmutableList<E>(element);
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any element is null
*/
public static <E> ImmutableList<E> 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 <E> ImmutableList<E> 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 <E> ImmutableList<E> 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 <E> ImmutableList<E> 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 <E> ImmutableList<E> 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 <E> ImmutableList<E> 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 <E> ImmutableList<E> 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 <E> ImmutableList<E> 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 <E> ImmutableList<E> 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 <E> ImmutableList<E> 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 <E> ImmutableList<E> 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.
*
* @deprecated use {@link #copyOf(Object[])}. <b>This method is scheduled for
* deletion in October 2011.</b>
* @throws NullPointerException if any of {@code elements} is null
* @since 2.0 (changed from varargs in 3.0)
*/
@Deprecated
public static <E> ImmutableList<E> of(E[] elements) {
return copyOf(elements);
}
/**
* 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 <E> ImmutableList<E> copyOf(Iterable<? extends E> 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.
*
* <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.
*
* <p>Note that if {@code list} is a {@code List<String>}, then {@code
* ImmutableList.copyOf(list)} returns an {@code ImmutableList<String>}
* containing each of the strings in {@code list}, while
* ImmutableList.of(list)} returns an {@code ImmutableList<List<String>>}
* containing one element (the given list itself).
*
* <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
*/
public static <E> ImmutableList<E> copyOf(Collection<? extends E> elements) {
if (elements instanceof ImmutableCollection) {
@SuppressWarnings("unchecked") // all supported methods are covariant
ImmutableList<E> list = ((ImmutableCollection<E>) 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 <E> ImmutableList<E> copyOf(Iterator<? extends E> elements) {
return copyFromCollection(Lists.newArrayList(elements));
}
/**
* Returns an immutable list containing the given elements, in order.
*
* @throws NullPointerException if any of {@code elements} is null
* @since 3.0
*/
public static <E> ImmutableList<E> copyOf(E[] elements) {
switch (elements.length) {
case 0:
return ImmutableList.of();
case 1:
return new SingletonImmutableList<E>(elements[0]);
default:
return construct(elements.clone());
}
}
private static <E> ImmutableList<E> copyFromCollection(
Collection<? extends E> collection) {
Object[] elements = collection.toArray();
switch (elements.length) {
case 0:
return of();
case 1:
@SuppressWarnings("unchecked") // collection had only Es in it
ImmutableList<E> list = new SingletonImmutableList<E>((E) elements[0]);
return list;
default:
// safe to use the array without copying it
// as specified by Collection.toArray().
return construct(elements);
}
}
/** {@code elements} has to be internally created array. */
private static <E> ImmutableList<E> construct(Object... elements) {
for (int i = 0; i < elements.length; i++) {
checkElementNotNull(elements[i], i);
}
return new RegularImmutableList<E>(elements);
}
// We do this instead of Preconditions.checkNotNull to save boxing and array
// creation cost.
private static Object checkElementNotNull(Object element, int index) {
if (element == null) {
throw new NullPointerException("at index " + index);
}
return element;
}
ImmutableList() {}
// This declaration is needed to make List.iterator() and
// ImmutableCollection.iterator() consistent.
@Override public UnmodifiableIterator<E> iterator() {
return listIterator();
}
@Override public UnmodifiableListIterator<E> listIterator() {
return listIterator(0);
}
@Override public abstract UnmodifiableListIterator<E> listIterator(int index);
// Mark these two methods with @Nullable
@Override
public abstract int indexOf(@Nullable Object object);
@Override
public abstract int lastIndexOf(@Nullable Object object);
// constrain the return type to ImmutableList<E>
/**
* 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 abstract ImmutableList<E> subList(int fromIndex, int toIndex);
/**
* Guaranteed to throw an exception and leave the list unmodified.
*
* @throws UnsupportedOperationException always
*/
@Override
public final boolean addAll(int index, Collection<? extends E> 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<E> 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<E> reverse() {
return new ReverseImmutableList<E>(this);
}
private static class ReverseImmutableList<E> extends ImmutableList<E> {
private transient final ImmutableList<E> forwardList;
private transient final int size;
ReverseImmutableList(ImmutableList<E> 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<E> 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<E> subList(int fromIndex, int toIndex) {
Preconditions.checkPositionIndexes(fromIndex, toIndex, size);
return forwardList.subList(
reversePosition(toIndex), reversePosition(fromIndex)).reverse();
}
@Override public E get(int index) {
Preconditions.checkElementIndex(index, size);
return forwardList.get(reverseIndex(index));
}
@Override public UnmodifiableListIterator<E> listIterator(int index) {
Preconditions.checkPositionIndex(index, size);
final UnmodifiableListIterator<E> forward =
forwardList.listIterator(reversePosition(index));
return new UnmodifiableListIterator<E>() {
@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 <E> Builder<E> builder() {
return new Builder<E>();
}
/**
* A builder for creating immutable list instances, especially {@code public
* static final} lists ("constant lists"). Example: <pre> {@code
*
* public static final ImmutableList<Color> GOOGLE_COLORS
* = new ImmutableList.Builder<Color>()
* .addAll(WEBSAFE_COLORS)
* .add(new Color(0, 191, 255))
* .build();}</pre>
*
* 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<E> extends ImmutableCollection.Builder<E> {
private final ArrayList<E> contents = Lists.newArrayList();
/**
* Creates a new builder. The returned builder is equivalent to the builder
* generated by {@link ImmutableList#builder}.
*/
public Builder() {}
/**
* 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<E> add(E element) {
contents.add(checkNotNull(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<E> addAll(Iterable<? extends E> elements) {
if (elements instanceof Collection) {
Collection<?> collection = (Collection<?>) elements;
contents.ensureCapacity(contents.size() + 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<E> add(E... elements) {
contents.ensureCapacity(contents.size() + elements.length);
super.add(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<E> addAll(Iterator<? extends E> elements) {
super.addAll(elements);
return this;
}
/**
* Returns a newly-created {@code ImmutableList} based on the contents of
* the {@code Builder}.
*/
@Override public ImmutableList<E> build() {
return copyOf(contents);
}
}
}
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