com.google.common.collect.ImmutableCollection Maven / Gradle / Ivy
/*
* Copyright (C) 2008 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 static com.google.common.collect.CollectPreconditions.checkNonnegative;
import static com.google.common.collect.ObjectArrays.checkElementsNotNull;
import com.google.common.annotations.GwtCompatible;
import java.io.Serializable;
import java.util.AbstractCollection;
import java.util.Collection;
import java.util.Iterator;
import javax.annotation.Nullable;
/**
* An immutable collection. Does not permit null elements.
*
* In addition to the {@link Collection} methods, this class has an {@link
* #asList()} method, which returns a list view of the collection's elements.
*
*
Note: Although this class is not final, it cannot be subclassed
* outside of this package as it has no public or protected constructors. Thus,
* instances of this type are guaranteed to be immutable.
*
* @author Jesse Wilson
* @since 2.0 (imported from Google Collections Library)
*/
@GwtCompatible(emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableCollection extends AbstractCollection
implements Serializable {
ImmutableCollection() {}
/**
* Returns an unmodifiable iterator across the elements in this collection.
*/
@Override
public abstract UnmodifiableIterator iterator();
@Override
public final Object[] toArray() {
int size = size();
if (size == 0) {
return ObjectArrays.EMPTY_ARRAY;
}
Object[] result = new Object[size];
copyIntoArray(result, 0);
return result;
}
@Override
public final T[] toArray(T[] other) {
checkNotNull(other);
int size = size();
if (other.length < size) {
other = ObjectArrays.newArray(other, size);
} else if (other.length > size) {
other[size] = null;
}
copyIntoArray(other, 0);
return other;
}
@Override
public boolean contains(@Nullable Object object) {
return object != null && super.contains(object);
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final boolean add(E e) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final boolean remove(Object object) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final boolean addAll(Collection newElements) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final boolean removeAll(Collection oldElements) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final boolean retainAll(Collection elementsToKeep) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final void clear() {
throw new UnsupportedOperationException();
}
/*
* TODO(kevinb): Restructure code so ImmutableList doesn't contain this
* variable, which it doesn't use.
*/
private transient ImmutableList asList;
/**
* Returns a list view of the collection.
*
* @since 2.0
*/
public ImmutableList asList() {
ImmutableList list = asList;
return (list == null) ? (asList = createAsList()) : list;
}
ImmutableList createAsList() {
switch (size()) {
case 0:
return ImmutableList.of();
case 1:
return ImmutableList.of(iterator().next());
default:
return new RegularImmutableAsList(this, toArray());
}
}
/**
* Returns {@code true} if this immutable collection's implementation contains references to
* user-created objects that aren't accessible via this collection's methods. This is generally
* used to determine whether {@code copyOf} implementations should make an explicit copy to avoid
* memory leaks.
*/
abstract boolean isPartialView();
/**
* Copies the contents of this immutable collection into the specified array at the specified
* offset. Returns {@code offset + size()}.
*/
int copyIntoArray(Object[] dst, int offset) {
for (E e : this) {
dst[offset++] = e;
}
return offset;
}
Object writeReplace() {
// We serialize by default to ImmutableList, the simplest thing that works.
return new ImmutableList.SerializedForm(toArray());
}
/**
* Abstract base class for builders of {@link ImmutableCollection} types.
*
* @since 10.0
*/
public abstract static class Builder {
static final int DEFAULT_INITIAL_CAPACITY = 4;
static int expandedCapacity(int oldCapacity, int minCapacity) {
if (minCapacity < 0) {
throw new AssertionError("cannot store more than MAX_VALUE elements");
}
// careful of overflow!
int newCapacity = oldCapacity + (oldCapacity >> 1) + 1;
if (newCapacity < minCapacity) {
newCapacity = Integer.highestOneBit(minCapacity - 1) << 1;
}
if (newCapacity < 0) {
newCapacity = Integer.MAX_VALUE;
// guaranteed to be >= newCapacity
}
return newCapacity;
}
Builder() {
}
/**
* Adds {@code element} to the {@code ImmutableCollection} being built.
*
* Note that each builder class covariantly returns its own type from
* this method.
*
* @param element the element to add
* @return this {@code Builder} instance
* @throws NullPointerException if {@code element} is null
*/
public abstract Builder add(E element);
/**
* Adds each element of {@code elements} to the {@code ImmutableCollection}
* being built.
*
* Note that each builder class overrides this method in order to
* covariantly return its own type.
*
* @param elements the elements to add
* @return this {@code Builder} instance
* @throws NullPointerException if {@code elements} is null or contains a
* null element
*/
public Builder add(E... elements) {
for (E element : elements) {
add(element);
}
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableCollection}
* being built.
*
* Note that each builder class overrides this method in order to
* covariantly return its own type.
*
* @param elements the elements to add
* @return this {@code Builder} instance
* @throws NullPointerException if {@code elements} is null or contains a
* null element
*/
public Builder addAll(Iterable elements) {
for (E element : elements) {
add(element);
}
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableCollection}
* being built.
*
* Note that each builder class overrides this method in order to
* covariantly return its own type.
*
* @param elements the elements to add
* @return this {@code Builder} instance
* @throws NullPointerException if {@code elements} is null or contains a
* null element
*/
public Builder addAll(Iterator elements) {
while (elements.hasNext()) {
add(elements.next());
}
return this;
}
/**
* Returns a newly-created {@code ImmutableCollection} of the appropriate
* type, containing the elements provided to this builder.
*
* Note that each builder class covariantly returns the appropriate type
* of {@code ImmutableCollection} from this method.
*/
public abstract ImmutableCollection build();
}
abstract static class ArrayBasedBuilder extends ImmutableCollection.Builder {
Object[] contents;
int size;
ArrayBasedBuilder(int initialCapacity) {
checkNonnegative(initialCapacity, "initialCapacity");
this.contents = new Object[initialCapacity];
this.size = 0;
}
/**
* Expand the absolute capacity of the builder so it can accept at least
* the specified number of elements without being resized.
*/
private void ensureCapacity(int minCapacity) {
if (contents.length < minCapacity) {
this.contents = ObjectArrays.arraysCopyOf(
this.contents, expandedCapacity(contents.length, minCapacity));
}
}
@Override
public ArrayBasedBuilder add(E element) {
checkNotNull(element);
ensureCapacity(size + 1);
contents[size++] = element;
return this;
}
@Override
public Builder add(E... elements) {
checkElementsNotNull(elements);
ensureCapacity(size + elements.length);
System.arraycopy(elements, 0, contents, size, elements.length);
size += elements.length;
return this;
}
@Override
public Builder addAll(Iterable elements) {
if (elements instanceof Collection) {
Collection collection = (Collection) elements;
ensureCapacity(size + collection.size());
}
super.addAll(elements);
return this;
}
}
}