/*
* 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.inject.internal.util;
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.ListIterator;
import java.util.NoSuchElementException;
import java.util.RandomAccess;
/**
* 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
*/
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableList<E> extends ImmutableCollection<E>
implements List<E>, RandomAccess {
private static final ImmutableList<?> EMPTY_IMMUTABLE_LIST
= new EmptyImmutableList();
/**
* 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>) EMPTY_IMMUTABLE_LIST;
}
/**
* 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) {
// TODO: evaluate a specialized SingletonImmutableList
return new RegularImmutableList<E>(copyIntoArray(element));
}
// TODO: Add similar overloadings to ImmutableSet and ImmutableSortedSet
/**
* 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 new RegularImmutableList<E>(copyIntoArray(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 new RegularImmutableList<E>(copyIntoArray(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 new RegularImmutableList<E>(copyIntoArray(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 new RegularImmutableList<E>(copyIntoArray(e1, e2, e3, e4, e5));
}
/**
* 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) {
return (elements.length == 0)
? ImmutableList.<E>of()
: new RegularImmutableList<E>(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<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><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.
*
* @throws NullPointerException if any of {@code elements} is null
*/
public static <E> ImmutableList<E> copyOf(Iterable<? extends E> 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<E> list = (ImmutableList<E>) elements;
return list;
} else if (elements instanceof Collection) {
@SuppressWarnings("unchecked")
Collection<? extends E> coll = (Collection<? extends E>) 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 <E> ImmutableList<E> copyOf(Iterator<? extends E> elements) {
return copyOfInternal(Lists.newArrayList(elements));
}
private static <E> ImmutableList<E> copyOfInternal(
ArrayList<? extends E> list) {
return (list.isEmpty())
? ImmutableList.<E>of()
: new RegularImmutableList<E>(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 <E> ImmutableList<E> copyOfInternal(
Collection<? extends E> collection) {
int size = collection.size();
return (size == 0)
? ImmutableList.<E>of()
: ImmutableList.<E>createFromIterable(collection, size);
}
private 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 final class EmptyImmutableList extends ImmutableList<Object> {
public int size() {
return 0;
}
@Override public boolean isEmpty() {
return true;
}
@Override public boolean contains(Object target) {
return false;
}
@Override public UnmodifiableIterator<Object> iterator() {
return Iterators.emptyIterator();
}
private static final Object[] EMPTY_ARRAY = new Object[0];
@Override public Object[] toArray() {
return EMPTY_ARRAY;
}
@Override public <T> T[] toArray(T[] a) {
if (a.length > 0) {
a[0] = null;
}
return a;
}
public Object get(int index) {
// guaranteed to fail, but at least we get a consistent message
Preconditions.checkElementIndex(index, 0);
throw new AssertionError("unreachable");
}
@Override public int indexOf(Object target) {
return -1;
}
@Override public int lastIndexOf(Object target) {
return -1;
}
@Override public ImmutableList<Object> subList(int fromIndex, int toIndex) {
Preconditions.checkPositionIndexes(fromIndex, toIndex, 0);
return this;
}
public ListIterator<Object> listIterator() {
return Iterators.emptyListIterator();
}
public ListIterator<Object> listIterator(int start) {
Preconditions.checkPositionIndex(start, 0);
return Iterators.emptyListIterator();
}
@Override public boolean containsAll(Collection<?> targets) {
return targets.isEmpty();
}
@Override public boolean equals(@Nullable Object object) {
if (object instanceof List) {
List<?> that = (List<?>) object;
return that.isEmpty();
}
return false;
}
@Override public int hashCode() {
return 1;
}
@Override public String toString() {
return "[]";
}
}
private static final class RegularImmutableList<E> extends ImmutableList<E> {
private final int offset;
private final int size;
private final Object[] array;
private RegularImmutableList(Object[] array, int offset, int size) {
this.offset = offset;
this.size = size;
this.array = array;
}
private RegularImmutableList(Object[] array) {
this(array, 0, array.length);
}
public int size() {
return size;
}
@Override public boolean isEmpty() {
return false;
}
@Override public boolean contains(Object target) {
return indexOf(target) != -1;
}
// The fake cast to E is safe because the creation methods only allow E's
@SuppressWarnings("unchecked")
@Override public UnmodifiableIterator<E> iterator() {
return (UnmodifiableIterator<E>) Iterators.forArray(array, offset, size);
}
@Override public Object[] toArray() {
Object[] newArray = new Object[size()];
System.arraycopy(array, offset, newArray, 0, size);
return newArray;
}
@Override public <T> T[] toArray(T[] other) {
if (other.length < size) {
other = ObjectArrays.newArray(other, size);
} else if (other.length > size) {
other[size] = null;
}
System.arraycopy(array, offset, other, 0, size);
return other;
}
// The fake cast to E is safe because the creation methods only allow E's
@SuppressWarnings("unchecked")
public E get(int index) {
Preconditions.checkElementIndex(index, size);
return (E) array[index + offset];
}
@Override public int indexOf(Object target) {
if (target != null) {
for (int i = offset; i < offset + size; i++) {
if (array[i].equals(target)) {
return i - offset;
}
}
}
return -1;
}
@Override public int lastIndexOf(Object target) {
if (target != null) {
for (int i = offset + size - 1; i >= offset; i--) {
if (array[i].equals(target)) {
return i - offset;
}
}
}
return -1;
}
@Override public ImmutableList<E> subList(int fromIndex, int toIndex) {
Preconditions.checkPositionIndexes(fromIndex, toIndex, size);
return (fromIndex == toIndex)
? ImmutableList.<E>of()
: new RegularImmutableList<E>(
array, offset + fromIndex, toIndex - fromIndex);
}
public ListIterator<E> listIterator() {
return listIterator(0);
}
public ListIterator<E> listIterator(final int start) {
Preconditions.checkPositionIndex(start, size);
return new ListIterator<E>() {
int index = start;
public boolean hasNext() {
return index < size;
}
public boolean hasPrevious() {
return index > 0;
}
public int nextIndex() {
return index;
}
public int previousIndex() {
return index - 1;
}
public E next() {
E result;
try {
result = get(index);
} catch (IndexOutOfBoundsException rethrown) {
throw new NoSuchElementException();
}
index++;
return result;
}
public E previous() {
E result;
try {
result = get(index - 1);
} catch (IndexOutOfBoundsException rethrown) {
throw new NoSuchElementException();
}
index--;
return result;
}
public void set(E o) {
throw new UnsupportedOperationException();
}
public void add(E o) {
throw new UnsupportedOperationException();
}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
@Override public boolean equals(@Nullable Object object) {
if (object == this) {
return true;
}
if (!(object instanceof List)) {
return false;
}
List<?> that = (List<?>) object;
if (this.size() != that.size()) {
return false;
}
int index = offset;
if (object instanceof RegularImmutableList) {
RegularImmutableList<?> other = (RegularImmutableList<?>) object;
for (int i = other.offset; i < other.offset + other.size; i++) {
if (!array[index++].equals(other.array[i])) {
return false;
}
}
} else {
for (Object element : that) {
if (!array[index++].equals(element)) {
return false;
}
}
}
return true;
}
@Override public int hashCode() {
// not caching hash code since it could change if the elements are mutable
// in a way that modifies their hash codes
int hashCode = 1;
for (int i = offset; i < offset + size; i++) {
hashCode = 31 * hashCode + array[i].hashCode();
}
return hashCode;
}
@Override public String toString() {
StringBuilder sb = new StringBuilder(size() * 16);
sb.append('[').append(array[offset]);
for (int i = offset + 1; i < offset + size; i++) {
sb.append(", ").append(array[i]);
}
return sb.append(']').toString();
}
}
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 <E> ImmutableList<E> 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();
}
if (index != estimatedSize) {
array = copyOf(array, index);
}
return new RegularImmutableList<E>(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 <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 class 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
*/
public Builder<E> add(E element) {
Preconditions.checkNotNull(element, "element cannot be null");
contents.add(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 or contains null
*/
public Builder<E> addAll(Iterable<? extends E> elements) {
if (elements instanceof Collection) {
@SuppressWarnings("unchecked")
Collection<? extends E> collection = (Collection<? extends E>) elements;
contents.ensureCapacity(contents.size() + collection.size());
}
for (E elem : elements) {
Preconditions.checkNotNull(elem, "elements contains a null");
contents.add(elem);
}
return this;
}
/**
* Returns a newly-created {@code ImmutableList} based on the contents of
* the {@code Builder}.
*/
public ImmutableList<E> build() {
return copyOf(contents);
}
}
}