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/*
* 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 static com.google.common.base.Preconditions.checkNotNull;
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.
*
* 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 ImmutableMap
* @see ImmutableSet
* @author Kevin Bourrillion
*/
@GwtCompatible(serializable = 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);
}
/**
* Identical to {@link #of(Object[])}.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(E e1, E e2) {
return new RegularImmutableList(copyIntoArray(e1, e2));
}
/**
* Identical to {@link #of(Object[])}.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(E e1, E e2, E e3) {
return new RegularImmutableList(copyIntoArray(e1, e2, e3));
}
/**
* Identical to {@link #of(Object[])}.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(E e1, E e2, E e3, E e4) {
return new RegularImmutableList(copyIntoArray(e1, e2, e3, e4));
}
/**
* Identical to {@link #of(Object[])}.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(E e1, E e2, E e3, E e4, E e5) {
return new RegularImmutableList(copyIntoArray(e1, e2, e3, e4, e5));
}
/**
* Identical to {@link #of(Object[])}.
*
* @throws NullPointerException if any element is null
*/
public static ImmutableList of(E e1, E e2, E e3, E e4, E e5, E e6) {
return new RegularImmutableList(copyIntoArray(e1, e2, e3, e4, e5, e6));
}
/**
* Identical to {@link #of(Object[])}.
*
* @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 new RegularImmutableList(
copyIntoArray(e1, e2, e3, e4, e5, e6, e7));
}
/**
* Identical to {@link #of(Object[])}.
*
* @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 new RegularImmutableList(
copyIntoArray(e1, e2, e3, e4, e5, e6, e7, e8));
}
/**
* Identical to {@link #of(Object[])}.
*
* @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 new RegularImmutableList(
copyIntoArray(e1, e2, e3, e4, e5, e6, e7, e8, e9));
}
/**
* Identical to {@link #of(Object[])}.
*
* @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 new RegularImmutableList(
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 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 new RegularImmutableList(
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 ImmutableList of(E... elements) {
checkNotNull(elements); // for GWT
switch (elements.length) {
case 0:
return ImmutableList.of();
case 1:
return new SingletonImmutableList(elements[0]);
default:
return new RegularImmutableList(copyIntoArray(elements));
}
}
/**
* Returns an immutable list containing the given elements, in order. This
* method iterates over {@code elements} at most once. 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).
*
* Note: 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.
*
* @throws NullPointerException if any of {@code elements} is null
*/
public static ImmutableList copyOf(Iterable elements) {
if (elements instanceof ImmutableList) {
/*
* TODO: If the given ImmutableList is a sublist, copy the referenced
* portion of the array into a new array to save space?
*/
@SuppressWarnings("unchecked") // all supported methods are covariant
ImmutableList list = (ImmutableList) elements;
return list;
} else if (elements instanceof Collection) {
@SuppressWarnings("unchecked")
Collection coll = (Collection) elements;
return copyOfInternal(coll);
} else {
return copyOfInternal(Lists.newArrayList(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) {
return copyOfInternal(Lists.newArrayList(elements));
}
private static ImmutableList copyOfInternal(
ArrayList list) {
switch (list.size()) {
case 0:
return of();
case 1:
return new SingletonImmutableList(list.iterator().next());
default:
return new RegularImmutableList(nullChecked(list.toArray()));
}
}
/**
* Checks that all the array elements are non-null.
*
* @return the argument array
* @throws NullPointerException if any element is null
*/
private static Object[] nullChecked(Object[] array) {
for (int i = 0, len = array.length; i < len; i++) {
if (array[i] == null) {
throw new NullPointerException("at index " + i);
}
}
return array;
}
private static ImmutableList copyOfInternal(
Collection collection) {
int size = collection.size();
return (size == 0)
? ImmutableList.of()
: ImmutableList.createFromIterable(collection, size);
}
ImmutableList() {}
// This declaration is needed to make List.iterator() and
// ImmutableCollection.iterator() consistent.
@Override public abstract UnmodifiableIterator 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
/**
* 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 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 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;
}
private static ImmutableList createFromIterable(
Iterable source, int estimatedSize) {
Object[] array = new Object[estimatedSize];
int index = 0;
for (Object element : source) {
if (index == estimatedSize) {
// At least one element was added after our call to size().
estimatedSize = ((estimatedSize / 2) + 1) * 3;
array = copyOf(array, estimatedSize);
}
if (element == null) {
throw new NullPointerException("at index " + index);
}
array[index++] = element;
}
if (index == 0) {
return of();
} else if (index == 1) {
// The elements of "array" come from a Iterable.
@SuppressWarnings("unchecked")
E element = (E) array[0];
return of(element);
}
if (index != estimatedSize) {
array = copyOf(array, index);
}
return new RegularImmutableList(array, 0, index);
}
// Avoid using Arrays.copyOf(), which is not present until JDK6.
private static Object[] copyOf(Object[] oldArray, int newSize) {
Object[] newArray = new Object[newSize];
System.arraycopy(oldArray, 0, newArray, 0,
Math.min(oldArray.length, newSize));
return newArray;
}
/*
* 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 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 the one created before it.
*/
public static final class Builder extends ImmutableCollection.Builder {
private final ArrayList 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 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 addAll(Iterable 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 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 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() {
return copyOf(contents);
}
}
}