Java tutorial
/* * Copyright (C) 2009 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.collect.Lists; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.Collections; import java.util.Iterator; import java.util.List; import java.util.RandomAccess; import javax.annotation.Nullable; /** * GWT emulated version of {@link ImmutableList}. * TODO(cpovirk): more doc * * @author Hayward Chan */ @SuppressWarnings("serial") // we're overriding default serialization public abstract class ImmutableList<E> extends ImmutableCollection<E> implements List<E>, RandomAccess { static final ImmutableList<Object> EMPTY = new RegularImmutableList<Object>(Collections.emptyList()); ImmutableList() { } // 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; } public static <E> ImmutableList<E> of(E element) { return new SingletonImmutableList<E>(element); } public static <E> ImmutableList<E> of(E e1, E e2) { return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(e1, e2)); } public static <E> ImmutableList<E> of(E e1, E e2, E e3) { return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(e1, e2, e3)); } public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4) { return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(e1, e2, e3, e4)); } public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5) { return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5)); } public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6) { return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6)); } public static <E> ImmutableList<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) { return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6, e7)); } 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>(ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6, e7, e8)); } 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>(ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6, e7, e8, e9)); } 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>( ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10)); } 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>( ImmutableList.<E>nullCheckedList(e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11)); } 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) { final int paramCount = 12; Object[] array = new Object[paramCount + others.length]; arrayCopy(array, 0, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11, e12); arrayCopy(array, paramCount, others); return new RegularImmutableList<E>(ImmutableList.<E>nullCheckedList(array)); } private static void arrayCopy(Object[] dest, int pos, Object... source) { System.arraycopy(source, 0, dest, pos, source.length); } public static <E> ImmutableList<E> copyOf(Iterable<? extends E> elements) { checkNotNull(elements); // for GWT return (elements instanceof Collection) ? copyOf((Collection<? extends E>) elements) : copyOf(elements.iterator()); } public static <E> ImmutableList<E> copyOf(Iterator<? extends E> elements) { return copyFromCollection(Lists.newArrayList(elements)); } public static <E> ImmutableList<E> copyOf(Collection<? extends E> elements) { if (elements instanceof ImmutableCollection) { /* * 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 ImmutableCollection<E> list = (ImmutableCollection<E>) elements; return list.asList(); } return copyFromCollection(elements); } public static <E> ImmutableList<E> copyOf(E[] elements) { checkNotNull(elements); // eager for GWT return copyOf(Arrays.asList(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>(ImmutableList.<E>nullCheckedList(elements)); } } // Factory method that skips the null checks. Used only when the elements // are guaranteed to be non-null. static <E> ImmutableList<E> unsafeDelegateList(List<? extends E> list) { switch (list.size()) { case 0: return of(); case 1: return new SingletonImmutableList<E>(list.iterator().next()); default: @SuppressWarnings("unchecked") List<E> castedList = (List<E>) list; return new RegularImmutableList<E>(castedList); } } /** * Views the array as an immutable list. The array must have only {@code E} elements. * * <p>The array must be internally created. */ @SuppressWarnings("unchecked") // caller is reponsible for getting this right static <E> ImmutableList<E> asImmutableList(Object[] elements) { return unsafeDelegateList((List) Arrays.asList(elements)); } private static <E> List<E> nullCheckedList(Object... array) { for (int i = 0, len = array.length; i < len; i++) { if (array[i] == null) { throw new NullPointerException("at index " + i); } } @SuppressWarnings("unchecked") E[] castedArray = (E[]) array; return Arrays.asList(castedArray); } @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); } public final boolean addAll(int index, Collection<? extends E> newElements) { throw new UnsupportedOperationException(); } public final E set(int index, E element) { throw new UnsupportedOperationException(); } public final void add(int index, E element) { throw new UnsupportedOperationException(); } public final E remove(int index) { throw new UnsupportedOperationException(); } @Override public UnmodifiableIterator<E> iterator() { return listIterator(); } @Override public ImmutableList<E> subList(int fromIndex, int toIndex) { return unsafeDelegateList(Lists.subListImpl(this, fromIndex, toIndex)); } @Override public UnmodifiableListIterator<E> listIterator() { return listIterator(0); } @Override public UnmodifiableListIterator<E> listIterator(int index) { return new AbstractIndexedListIterator<E>(size(), index) { @Override protected E get(int index) { return ImmutableList.this.get(index); } }; } @Override public ImmutableList<E> asList() { return this; } @Override public boolean equals(@Nullable Object obj) { return Lists.equalsImpl(this, obj); } @Override public int hashCode() { return Lists.hashCodeImpl(this); } public ImmutableList<E> reverse() { List<E> list = Lists.newArrayList(this); Collections.reverse(list); return unsafeDelegateList(list); } public static <E> Builder<E> builder() { return new Builder<E>(); } public static final class Builder<E> extends ImmutableCollection.Builder<E> { private final ArrayList<E> contents; public Builder() { contents = Lists.newArrayList(); } Builder(int capacity) { contents = Lists.newArrayListWithCapacity(capacity); } @Override public Builder<E> add(E element) { contents.add(checkNotNull(element)); return this; } @Override public Builder<E> addAll(Iterable<? extends E> elements) { super.addAll(elements); return this; } @Override public Builder<E> add(E... elements) { checkNotNull(elements); // for GWT super.add(elements); return this; } @Override public Builder<E> addAll(Iterator<? extends E> elements) { super.addAll(elements); return this; } @Override public ImmutableList<E> build() { return copyOf(contents); } } }