/*
* Copyright (C) 2007 Google Inc.
*
* 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 com.google.common.annotations.GwtCompatible;
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;
import static com.google.common.base.Preconditions.checkNotNull;
/**
* 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 2010.01.04 <b>stable</b> (imported from Google Collections Library)
*/
@GwtCompatible(serializable = 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() {
// BEGIN android-changed
return (ImmutableList) EmptyImmutableList.INSTANCE;
// END android-changed
}
/**
* 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);
}
/**
* Identical to {@link #of(Object[])}.
*
* @throws NullPointerException if any element is null
*/
public static <E> ImmutableList<E> of(E e1, E e2) {
return new RegularImmutableList<E>(copyIntoArray(e1, e2));
}
/**
* Identical to {@link #of(Object[])}.
*
* @throws NullPointerException if any element is null
*/
public static <E> ImmutableList<E> of(E e1, E e2, E e3) {
return new RegularImmutableList<E>(copyIntoArray(e1, e2, e3));
}
/**
* Identical to {@link #of(Object[])}.
*
* @throws NullPointerException if any element is null
*/
public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4) {
return new RegularImmutableList<E>(copyIntoArray(e1, e2, e3, e4));
}
/**
* Identical to {@link #of(Object[])}.
*
* @throws NullPointerException if any element is null
*/
public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5) {
return new RegularImmutableList<E>(copyIntoArray(e1, e2, e3, e4, e5));
}
/**
* Identical to {@link #of(Object[])}.
*
* @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 new RegularImmutableList<E>(copyIntoArray(e1, e2, e3, e4, e5, e6));
}
/**
* Identical to {@link #of(Object[])}.
*
* @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 new RegularImmutableList<E>(
copyIntoArray(e1, e2, e3, e4, e5, e6, e7));
}
/**
* Identical to {@link #of(Object[])}.
*
* @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 new RegularImmutableList<E>(
copyIntoArray(e1, e2, e3, e4, e5, e6, e7, e8));
}
/**
* Identical to {@link #of(Object[])}.
*
* @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 new RegularImmutableList<E>(
copyIntoArray(e1, e2, e3, e4, e5, e6, e7, e8, e9));
}
/**
* Identical to {@link #of(Object[])}.
*
* @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 new RegularImmutableList<E>(
copyIntoArray(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10));
}
/**
* Identical to {@link #of(Object[])}.
*
* @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 new RegularImmutableList<E>(
copyIntoArray(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 of {@code elements} is null
*/
public static <E> ImmutableList<E> of(E... elements) {
checkNotNull(elements); // for GWT
switch (elements.length) {
case 0:
return ImmutableList.of();
case 1:
return new SingletonImmutableList<E>(elements[0]);
default:
return new RegularImmutableList<E>(copyIntoArray(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
*/
@SuppressWarnings("unchecked") // bugs.sun.com/view_bug.do?bug_id=6558557
public static <E> ImmutableList<E> copyOf(Iterable<? extends E> elements) {
checkNotNull(elements);
return (elements instanceof Collection)
? copyOf((Collection<? extends E>) elements)
: copyOf(elements.iterator());
}
/**
* Returns an immutable list containing the given elements, in order.
*
* <p><b>Note:</b> Despite what the method name suggests, if {@code elements}
* is an {@code ImmutableList}, no copy will actually be performed, and the
* given list itself will be returned.
*
* <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
* @since 2010.01.04 <b>stable</b> (Iterable overload existed previously)
*/
public static <E> ImmutableList<E> copyOf(Collection<? extends E> elements) {
checkNotNull(elements);
// TODO: Once the ImmutableAsList and ImmutableSortedAsList are
// GWT-compatible, return elements.asList() when elements is an
// ImmutableCollection.
if (elements instanceof ImmutableList) {
/*
* TODO: When given an ImmutableList that's a sublist, copy the referenced
* portion of the array into a new array to save space?
*/
@SuppressWarnings("unchecked") // all supported methods are covariant
ImmutableList<E> list = (ImmutableList<E>) elements;
return 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));
}
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:
return new RegularImmutableList<E>(copyIntoArray(elements));
}
}
ImmutableList() {}
// This declaration is needed to make List.iterator() and
// ImmutableCollection.iterator() consistent.
@Override public abstract UnmodifiableIterator<E> iterator();
// Mark these two methods with @Nullable
public abstract int indexOf(@Nullable Object object);
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.)
*/
public abstract ImmutableList<E> subList(int fromIndex, int toIndex);
/**
* Guaranteed to throw an exception and leave the list unmodified.
*
* @throws UnsupportedOperationException always
*/
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
*/
public final E set(int index, E element) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the list unmodified.
*
* @throws UnsupportedOperationException always
*/
public final void add(int index, E element) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the list unmodified.
*
* @throws UnsupportedOperationException always
*/
public final E remove(int index) {
throw new UnsupportedOperationException();
}
private static Object[] copyIntoArray(Object... source) {
Object[] array = new Object[source.length];
int index = 0;
for (Object element : source) {
if (element == null) {
throw new NullPointerException("at index " + index);
}
array[index++] = element;
}
return array;
}
/**
* Returns this list instance.
*
* @since 2010.01.04 <b>tentative</b>
*/
@Override public ImmutableList<E> asList() {
return 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 of(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").
*
* <p>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>
*
* <p>Builder instances can be reused - it is safe to call {@link #build}
* multiple times to build multiple lists in series. Each new list
* contains the one created before it.
*/
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) {
checkNotNull(elements); // for GWT
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);
}
}
}