/*
* Copyright (C) 2008 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.base.Nullable;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.SortedSet;
/**
* An immutable {@code SortedSet} that stores its elements in a sorted array.
* Some instances are ordered by an explicit comparator, while others follow the
* natural sort ordering of their elements. Either way, null elements are not
* supported.
*
* Unlike {@link Collections#unmodifiableSortedSet}, which is a view
* of a separate collection that can still change, an instance of {@code
* ImmutableSortedSet} contains its own private data and will never
* change. This class is convenient for {@code public static final} sets
* ("constant sets") and also lets you easily make a "defensive copy" of a set
* provided to your class by a caller.
*
*
The sets returned by {@link #headSet}, {@link #tailSet}, and
* {@link #subSet} methods share the same array as the original set, preventing
* that array from being garbage collected. If this is a concern, the data may
* be copied into a correctly-sized array by calling {@link #copyOfSorted}.
*
*
Note on element equivalence: The {@link #contains(Object)},
* {@link #containsAll(Collection)}, and {@link #equals(Object)}
* implementations must check whether a provided object is equivalent to an
* element in the collection. Unlike most collections, an
* {@code ImmutableSortedSet} doesn't use {@link Object#equals} to determine if
* two elements are equivalent. Instead, with an explicit comparator, the
* following relation determines whether elements {@code x} and {@code y} are
* equivalent:
{@code
*
* {(x, y) | comparator.compare(x, y) == 0}}
*
* With natural ordering of elements, the following relation determines whether
* two elements are equivalent: {@code
*
* {(x, y) | x.compareTo(y) == 0}}
*
* Warning: Like most sets, an {@code ImmutableSortedSet} will not
* function correctly if an element is modified after being placed in the set.
* For this reason, and to avoid general confusion, it is strongly recommended
* to place only immutable objects into this collection.
*
* 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 ImmutableSet
* @author Jared Levy
*/
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableSortedSet extends ImmutableSet
implements SortedSet {
// TODO: Can we find a way to remove these @SuppressWarnings?
@SuppressWarnings("unchecked")
private static final Comparator NATURAL_ORDER = Ordering.natural();
@SuppressWarnings("unchecked")
private static final ImmutableSortedSet NATURAL_EMPTY_SET =
new EmptyImmutableSortedSet(NATURAL_ORDER);
@SuppressWarnings("unchecked")
private static ImmutableSortedSet emptySet() {
return (ImmutableSortedSet) NATURAL_EMPTY_SET;
}
private static ImmutableSortedSet emptySet(
Comparator comparator) {
if (comparator == NATURAL_ORDER) {
return emptySet();
} else {
return new EmptyImmutableSortedSet(comparator);
}
}
/**
* Returns the empty immutable sorted set.
*/
public static ImmutableSortedSet of() {
return emptySet();
}
/**
* Returns an immutable sorted set containing a single element.
*
* The type specification is {@code }, instead of the
* more specific {@code >}, to support
* classes defined without generics.
*/
@SuppressWarnings("unchecked") // See method Javadoc
public static ImmutableSortedSet of(E element) {
Object[] array = { checkNotNull(element) };
return new RegularImmutableSortedSet(array, NATURAL_ORDER);
}
// TODO: Consider adding factory methods that throw an exception when given
// duplicate elements.
/**
* Returns an immutable sorted set containing the given elements sorted by
* their natural ordering. When multiple elements are equivalent according to
* {@link Comparable#compareTo}, only the first one specified is included.
*
* The type specification is {@code }, instead of the
* more specific {@code >}, to support
* classes defined without generics.
*
* @throws NullPointerException if any of {@code elements} is null
*/
@SuppressWarnings("unchecked") // See method Javadoc
public static ImmutableSortedSet of(E... elements) {
return ofInternal(Ordering.natural(), elements);
}
private static ImmutableSortedSet ofInternal(
Comparator comparator, E... elements) {
switch (elements.length) {
case 0:
return emptySet(comparator);
default:
Object[] array = Platform.clone(elements);
for (Object element : array) {
checkNotNull(element);
}
sort(array, comparator);
array = removeDupes(array, comparator);
return new RegularImmutableSortedSet(array, comparator);
}
}
/** Sort the array, according to the comparator. */
@SuppressWarnings("unchecked") // E comparator with Object array
private static void sort(
Object[] array, Comparator comparator) {
Arrays.sort(array, (Comparator) comparator);
}
/**
* Returns an array that removes duplicate consecutive elements, according to
* the provided comparator. Note that the input array is modified. This method
* does not support empty arrays.
*/
private static Object[] removeDupes(Object[] array,
Comparator comparator) {
int size = 1;
for (int i = 1; i < array.length; i++) {
Object element = array[i];
if ((compare(comparator, array[size - 1], element) != 0)) {
array[size] = element;
size++;
}
}
// TODO: Move to ObjectArrays?
if (size == array.length) {
return array;
} else {
Object[] copy = new Object[size];
System.arraycopy(array, 0, copy, 0, size);
return copy;
}
}
/**
* Returns an immutable sorted set containing the given elements sorted by
* their natural ordering. When multiple elements are equivalent according to
* {@code compareTo()}, only the first one specified is included. To create a
* copy of a {@code SortedSet} that preserves the comparator, call
* {@link #copyOfSorted} instead. This method iterates over {@code elements}
* at most once.
*
* Note that if {@code s} is a {@code Set}, then
* {@code ImmutableSortedSet.copyOf(s)} returns a
* {@code ImmutableSortedSet} containing each of the strings in
* {@code s}, while {@code ImmutableSortedSet.of(s)} returns a
* {@code ImmutableSortedSet>} containing one element (the given
* set itself).
*
* Note: Despite what the method name suggests, if {@code elements}
* is an {@code ImmutableSortedSet}, it may be returned instead of a copy.
*
*
The type specification is {@code }, instead of the
* more specific {@code >}, to support
* classes defined without generics.
*
* @throws NullPointerException if any of {@code elements} is null
*/
@SuppressWarnings("unchecked")
public static ImmutableSortedSet copyOf(
Iterable elements) {
return copyOfInternal(Ordering.natural(), elements, false);
}
/**
* Returns an immutable sorted set containing the given elements sorted by
* their natural ordering. When multiple elements are equivalent according to
* {@code compareTo()}, only the first one specified is included.
*
* The type specification is {@code }, instead of the
* more specific {@code >}, to support
* classes defined without generics.
*
* @throws NullPointerException if any of {@code elements} is null
*/
@SuppressWarnings("unchecked")
public static ImmutableSortedSet copyOf(
Iterator elements) {
return copyOfInternal(Ordering.natural(), elements);
}
/**
* Returns an immutable sorted set containing the elements of a sorted set,
* sorted by the same {@code Comparator}. That behavior differs from
* {@link #copyOf(Iterable)}, which always uses the natural ordering of the
* elements.
*
* Note: Despite what the method name suggests, if {@code sortedSet}
* is an {@code ImmutableSortedSet}, it may be returned instead of a copy.
*
* @throws NullPointerException if any of {@code elements} is null
*/
@SuppressWarnings("unchecked")
public static ImmutableSortedSet copyOfSorted(SortedSet sortedSet) {
Comparator comparator = sortedSet.comparator();
if (comparator == null) {
comparator = NATURAL_ORDER;
}
return copyOfInternal(comparator, sortedSet, true);
}
private static ImmutableSortedSet copyOfInternal(
Comparator comparator, Iterable elements,
boolean fromSortedSet) {
boolean hasSameComparator
= fromSortedSet || hasSameComparator(elements, comparator);
if (hasSameComparator && (elements instanceof ImmutableSortedSet)) {
@SuppressWarnings("unchecked")
ImmutableSortedSet result = (ImmutableSortedSet) elements;
if (!result.hasPartialArray()) {
return result;
}
}
@SuppressWarnings("unchecked")
Object[] array
= Iterables.newArray((Iterable) elements, Object.class);
if (array.length == 0) {
return emptySet(comparator);
}
for (Object e : array) {
checkNotNull(e);
}
if (!hasSameComparator) {
sort(array, comparator);
array = removeDupes(array, comparator);
}
return new RegularImmutableSortedSet(array, comparator);
}
private static ImmutableSortedSet copyOfInternal(
Comparator comparator, Iterator elements) {
if (!elements.hasNext()) {
return emptySet(comparator);
}
List list = Lists.newArrayList();
while (elements.hasNext()) {
list.add(checkNotNull(elements.next()));
}
Object[] array = list.toArray();
sort(array, comparator);
array = removeDupes(array, comparator);
return new RegularImmutableSortedSet(array, comparator);
}
/**
* Returns {@code true} if {@code elements} is a {@code SortedSet} that uses
* {@code comparator} to order its elements. Note that equivalent comparators
* may still return {@code false}, if {@code equals} doesn't consider them
* equal. If one comparator is {@code null} and the other is
* {@link Ordering#natural()}, this method returns {@code true}.
*/
private static boolean hasSameComparator(
Iterable elements, Comparator comparator) {
if (elements instanceof SortedSet) {
SortedSet sortedSet = (SortedSet) elements;
Comparator comparator2 = sortedSet.comparator();
return (comparator2 == null)
? comparator == Ordering.natural()
: comparator.equals(comparator2);
}
return false;
}
/**
* Returns a builder that creates immutable sorted sets with an explicit
* comparator. If the comparator has a more general type than the set being
* generated, such as creating a {@code SortedSet} with a
* {@code Comparator}, use the {@link Builder} constructor instead.
*
* @throws NullPointerException if {@code comparator} is null
*/
public static Builder orderedBy(Comparator comparator) {
return new Builder(comparator);
}
/**
* Returns a builder that creates immutable sorted sets whose elements are
* ordered by the reverse of their natural ordering. The sorted sets use
* {@link Collections#reverseOrder()} as the comparator.
*
* The type specification is {@code }, instead of the
* more specific {@code >}, to support
* classes defined without generics.
*/
@SuppressWarnings("unchecked") // See method Javadoc
public static Builder reverseOrder() {
return new Builder(Collections.reverseOrder());
}
/**
* Returns a builder that creates immutable sorted sets whose elements are
* ordered by their natural ordering. The sorted sets use
* {@link Ordering#natural()} as the comparator. This method provides
* more type-safety than {@link #builder()}, as it can be called only for
* classes that implement {@link Comparable}.
*
* The type specification is {@code }, instead of the
* more specific {@code >}, to support
* classes defined without generics.
*/
@SuppressWarnings("unchecked") // See method Javadoc
public static Builder naturalOrder() {
return new Builder(Ordering.natural());
}
/**
* Not supported. Use {@link #naturalOrder()}, which offers better
* type-safety, instead. This method exists only to hide
* {@link ImmutableSet#builder()} from consumers of
* {@code ImmutableSortedSet}.
*
* @throws UnsupportedOperationException always
*
* @deprecated Use {@link #naturalOrder()}, which offers better type-safety.
*/
@Deprecated public static Builder builder() {
throw new UnsupportedOperationException();
}
/**
* A builder for creating immutable sorted set instances, especially
* {@code public static final} sets ("constant sets"), with a given
* comparator.
*
* Example:
*
{@code
* public static final ImmutableSortedSet LUCKY_NUMBERS
* = new ImmutableSortedSet.Builder(ODDS_FIRST_COMPARATOR)
* .addAll(SINGLE_DIGIT_PRIMES)
* .add(42)
* .build();}
*
* Builder instances can be reused - it is safe to call {@link #build}
* multiple times to build multiple sets in series. Each set
* is a superset of the set created before it.
*/
public static class Builder extends ImmutableSet.Builder {
private final Comparator comparator;
/**
* Creates a new builder. The returned builder is equivalent to the builder
* generated by {@link ImmutableSortedSet#orderedBy}.
*/
public Builder(Comparator comparator) {
this.comparator = checkNotNull(comparator);
}
/**
* Adds {@code element} to the {@code ImmutableSortedSet}. If the
* {@code ImmutableSortedSet} already contains {@code element}, then
* {@code add} has no effect. (only the previously added element
* is retained).
*
* @param element the element to add
* @return this {@code Builder} object
* @throws NullPointerException if {@code element} is null
*/
@Override public Builder add(E element) {
super.add(element);
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableSortedSet},
* ignoring duplicate elements (only the first duplicate element is added).
*
* @param elements the elements to add
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is or contains null
*/
@Override public Builder add(E... elements) {
super.add(elements);
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableSortedSet},
* ignoring duplicate elements (only the first duplicate element is added).
*
* @param elements the elements to add to the {@code ImmutableSortedSet}
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is or contains null
*/
@Override public Builder addAll(Iterable elements) {
super.addAll(elements);
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableSortedSet},
* ignoring duplicate elements (only the first duplicate element is added).
*
* @param elements the elements to add to the {@code ImmutableSortedSet}
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is or contains null
*/
@Override public Builder addAll(Iterator elements) {
super.addAll(elements);
return this;
}
/**
* Returns a newly-created {@code ImmutableSortedSet} based on the contents
* of the {@code Builder} and its comparator.
*/
@Override public ImmutableSortedSet build() {
return copyOfInternal(comparator, contents.iterator());
}
}
@SuppressWarnings("unchecked")
private static int compare(Comparator comparator, Object a,
Object b) {
return comparator.compare((E) a, (E) b);
}
final Comparator comparator;
private ImmutableSortedSet(Comparator comparator) {
this.comparator = comparator;
}
/**
* Returns the comparator that orders the elements, which is
* {@link Ordering#natural()} when the natural ordering of the
* elements is used. Note that its behavior is not consistent with
* {@link SortedSet#comparator()}, which returns {@code null} to indicate
* natural ordering.
*/
public Comparator comparator() {
return comparator;
}
/**
* {@inheritDoc}
*
* This method returns a serializable {@code ImmutableSortedSet}.
*
*
The {@link SortedSet#headSet} documentation states that a subset of a
* subset throws an {@link IllegalArgumentException} if passed a
* {@code toElement} greater than an earlier {@code toElement}. However, this
* method doesn't throw an exception in that situation, but instead keeps the
* original {@code toElement}.
*/
public ImmutableSortedSet headSet(E toElement) {
return headSetImpl(checkNotNull(toElement));
}
/**
* {@inheritDoc}
*
* This method returns a serializable {@code ImmutableSortedSet}.
*
*
The {@link SortedSet#subSet} documentation states that a subset of a
* subset throws an {@link IllegalArgumentException} if passed a
* {@code fromElement} smaller than an earlier {@code toElement}. However,
* this method doesn't throw an exception in that situation, but instead keeps
* the original {@code fromElement}. Similarly, this method keeps the
* original {@code toElement}, instead of throwing an exception, if passed a
* {@code toElement} greater than an earlier {@code toElement}.
*/
public ImmutableSortedSet subSet(E fromElement, E toElement) {
checkNotNull(fromElement);
checkNotNull(toElement);
checkArgument(compare(comparator, fromElement, toElement) <= 0);
return subSetImpl(fromElement, toElement);
}
/**
* {@inheritDoc}
*
* This method returns a serializable {@code ImmutableSortedSet}.
*
*
The {@link SortedSet#tailSet} documentation states that a subset of a
* subset throws an {@link IllegalArgumentException} if passed a
* {@code fromElement} smaller than an earlier {@code fromElement}. However,
* this method doesn't throw an exception in that situation, but instead keeps
* the original {@code fromElement}.
*/
public ImmutableSortedSet tailSet(E fromElement) {
return tailSetImpl(checkNotNull(fromElement));
}
/*
* These methods perform most headSet, subSet, and tailSet logic, besides
* parameter validation.
*/
abstract ImmutableSortedSet headSetImpl(E toElement);
abstract ImmutableSortedSet subSetImpl(E fromElement, E toElement);
abstract ImmutableSortedSet tailSetImpl(E fromElement);
/** Returns whether the elements are stored in a subset of a larger array. */
abstract boolean hasPartialArray();
/** An empty immutable sorted set. */
private static class EmptyImmutableSortedSet
extends ImmutableSortedSet {
EmptyImmutableSortedSet(Comparator comparator) {
super(comparator);
}
public int size() {
return 0;
}
@Override public boolean isEmpty() {
return true;
}
@Override public boolean contains(Object target) {
return false;
}
@Override public UnmodifiableIterator iterator() {
return Iterators.emptyIterator();
}
private static final Object[] EMPTY_ARRAY = new Object[0];
@Override public Object[] toArray() {
return EMPTY_ARRAY;
}
@Override public T[] toArray(T[] a) {
if (a.length > 0) {
a[0] = null;
}
return a;
}
@Override public boolean containsAll(Collection targets) {
return targets.isEmpty();
}
@Override public boolean equals(@Nullable Object object) {
if (object instanceof Set) {
Set that = (Set) object;
return that.isEmpty();
}
return false;
}
@Override public int hashCode() {
return 0;
}
@Override public String toString() {
return "[]";
}
public E first() {
throw new NoSuchElementException();
}
public E last() {
throw new NoSuchElementException();
}
@Override ImmutableSortedSet headSetImpl(E toElement) {
return this;
}
@Override ImmutableSortedSet subSetImpl(E fromElement, E toElement) {
return this;
}
@Override ImmutableSortedSet tailSetImpl(E fromElement) {
return this;
}
@Override boolean hasPartialArray() {
return false;
}
}
/**
* An empty immutable sorted set with one or more elements.
* TODO: Consider creating a separate class for a single-element sorted set.
*/
@SuppressWarnings("serial")
private static final class RegularImmutableSortedSet
extends ImmutableSortedSet {
final Object[] elements;
/**
* The index of the first element that's in the sorted set (inclusive
* index).
*/
final int fromIndex;
/**
* The index after the last element that's in the sorted set (exclusive
* index).
*/
final int toIndex;
RegularImmutableSortedSet(Object[] elements,
Comparator comparator) {
super(comparator);
this.elements = elements;
this.fromIndex = 0;
this.toIndex = elements.length;
}
RegularImmutableSortedSet(Object[] elements,
Comparator comparator, int fromIndex, int toIndex) {
super(comparator);
this.elements = elements;
this.fromIndex = fromIndex;
this.toIndex = toIndex;
}
// The factory methods ensure that every element is an E.
@SuppressWarnings("unchecked")
@Override public UnmodifiableIterator iterator() {
return (UnmodifiableIterator)
Iterators.forArray(elements, fromIndex, size());
}
@Override public boolean isEmpty() {
return false;
}
public int size() {
return toIndex - fromIndex;
}
@Override public boolean contains(Object o) {
if (o == null) {
return false;
}
try {
return binarySearch(o) >= 0;
} catch (ClassCastException e) {
return false;
}
}
@Override public boolean containsAll(Collection targets) {
// TODO: For optimal performance, use a binary search when
// targets.size() < size() / log(size())
if (!hasSameComparator(targets, comparator()) || (targets.size() <= 1)) {
return super.containsAll(targets);
}
/*
* If targets is a sorted set with the same comparator, containsAll can
* run in O(n) time stepping through the two collections.
*/
int i = fromIndex;
Iterator iterator = targets.iterator();
Object target = iterator.next();
while (true) {
if (i >= toIndex) {
return false;
}
int cmp = compare(comparator, elements[i], target);
if (cmp < 0) {
i++;
} else if (cmp == 0) {
if (!iterator.hasNext()) {
return true;
}
target = iterator.next();
i++;
} else if (cmp > 0) {
return false;
}
}
}
int binarySearch(Object key) {
int lower = fromIndex;
int upper = toIndex - 1;
while (lower <= upper) {
int middle = lower + (upper - lower) / 2;
int c = compare(comparator, key, elements[middle]);
if (c < 0) {
upper = middle - 1;
} else if (c > 0) {
lower = middle + 1;
} else {
return middle;
}
}
return -lower - 1;
}
@Override public Object[] toArray() {
Object[] array = new Object[size()];
System.arraycopy(elements, fromIndex, array, 0, size());
return array;
}
// TODO: Move to ObjectArrays (same code in ImmutableList).
@Override public T[] toArray(T[] array) {
int size = size();
if (array.length < size) {
array = ObjectArrays.newArray(array, size);
} else if (array.length > size) {
array[size] = null;
}
System.arraycopy(elements, fromIndex, array, 0, size);
return array;
}
@Override public boolean equals(@Nullable Object object) {
if (object == this) {
return true;
}
if (!(object instanceof Set)) {
return false;
}
Set that = (Set) object;
if (size() != that.size()) {
return false;
}
if (hasSameComparator(that, comparator)) {
Iterator iterator = that.iterator();
try {
for (int i = fromIndex; i < toIndex; i++) {
Object otherElement = iterator.next();
if (otherElement == null
|| compare(comparator, elements[i], otherElement) != 0) {
return false;
}
}
return true;
} catch (ClassCastException e) {
return false;
} catch (NoSuchElementException e) {
return false; // concurrent change to other set
}
}
return this.containsAll(that);
}
@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 hash = 0;
for (int i = fromIndex; i < toIndex; i++) {
hash += elements[i].hashCode();
}
return hash;
}
@Override public String toString() {
StringBuilder result = new StringBuilder(size() * 16);
result.append('[').append(elements[fromIndex]);
for (int i = fromIndex + 1; i < toIndex; i++) {
result.append(", ").append(elements[i]);
}
return result.append(']').toString();
}
// The factory methods ensure that every element is an E.
@SuppressWarnings("unchecked")
public E first() {
return (E) elements[fromIndex];
}
// The factory methods ensure that every element is an E.
@SuppressWarnings("unchecked")
public E last() {
return (E) elements[toIndex - 1];
}
@Override ImmutableSortedSet headSetImpl(E toElement) {
return createSubset(fromIndex, findSubsetIndex(toElement));
}
@Override ImmutableSortedSet subSetImpl(E fromElement, E toElement) {
return createSubset(
findSubsetIndex(fromElement), findSubsetIndex(toElement));
}
@Override ImmutableSortedSet tailSetImpl(E fromElement) {
return createSubset(findSubsetIndex(fromElement), toIndex);
}
int findSubsetIndex(E fromElement) {
int index = binarySearch(fromElement);
return (index >= 0) ? index : (-index - 1);
}
ImmutableSortedSet createSubset(int newFromIndex, int newToIndex) {
if (newFromIndex < newToIndex) {
return new RegularImmutableSortedSet(elements, comparator,
newFromIndex, newToIndex);
} else {
return emptySet(comparator);
}
}
@Override boolean hasPartialArray() {
return (fromIndex != 0) || (toIndex != elements.length);
}
}
/*
* This class is used to serialize all ImmutableSortedSet instances,
* regardless of implementation type. It captures their "logical contents"
* only. This is necessary to ensure that the existence of a particular
* implementation type is an implementation detail.
*/
private static class SerializedForm implements Serializable {
final Comparator comparator;
final Object[] elements;
public SerializedForm(Comparator comparator, Object[] elements) {
this.comparator = comparator;
this.elements = elements;
}
@SuppressWarnings("unchecked")
Object readResolve() {
return new Builder(comparator).add((E[]) elements).build();
}
private static final long serialVersionUID = 0;
}
private void readObject(ObjectInputStream stream)
throws InvalidObjectException {
throw new InvalidObjectException("Use SerializedForm");
}
@Override Object writeReplace() {
return new SerializedForm(comparator, toArray());
}
}
