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A lightweight alternative to Java 8 sequential Stream
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/*
* Copyright 2016 Daniel Skogquist Åborg
*
* 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 org.d2ab.collection;
import org.d2ab.iterator.Iterators;
import java.util.*;
import java.util.function.Predicate;
/**
* A {@link Collection} view of an {@link Iterable}, requiring only {@link Iterable#iterator()} to be implemented in
* order to present a full {@link Collection}. This interface is thus a functional interface of {@link Iterable}'s
* {@link Iterable#iterator()} method. All methods are implemented through {@link Iterator} traversal of the underlying
* {@link Iterable}. All methods are supported except {@link #add(Object)} and {@link #addAll(Collection)}.
*/
@FunctionalInterface
public interface IterableCollection extends Collection, SizedIterable {
static IterableCollection empty() {
return from(Iterables.empty());
}
static IterableCollection of(T t) {
return from(Iterables.of(t));
}
@SafeVarargs
static IterableCollection of(T... ts) {
return from(Iterables.of(ts));
}
static IterableCollection from(Iterable iterable) {
if (iterable instanceof SizedIterable)
return from((SizedIterable) iterable);
if (iterable instanceof Collection)
return from((Collection) iterable);
return iterable::iterator;
}
static IterableCollection from(Collection collection) {
SizeType sizeType = Iterables.sizeType(collection);
return new IterableCollection() {
@Override
public Iterator iterator() {
return collection.iterator();
}
@Override
public int size() {
return collection.size();
}
@Override
public SizeType sizeType() {
return sizeType;
}
@Override
public boolean isEmpty() {
return collection.isEmpty();
}
};
}
static IterableCollection from(SizedIterable iterable) {
return new IterableCollection() {
@Override
public Iterator iterator() {
return iterable.iterator();
}
@Override
public int size() {
return iterable.size();
}
@Override
public SizeType sizeType() {
return iterable.sizeType();
}
@Override
public boolean isEmpty() {
return iterable.isEmpty();
}
};
}
@Override
default int size() {
return SizedIterable.size(this);
}
@Override
default boolean isEmpty() {
return SizedIterable.isEmpty(this);
}
@Override
default boolean contains(Object o) {
return Iterators.contains(iterator(), o);
}
@Override
default Object[] toArray() {
return Iterators.toList(iterator()).toArray();
}
@Override
default TT[] toArray(TT[] a) {
return Iterators.toList(iterator()).toArray(a);
}
@Override
default boolean add(T t) {
throw new UnsupportedOperationException();
}
@Override
default boolean remove(Object o) {
Iterator iterator = iterator();
while (iterator.hasNext())
if (Objects.equals(o, iterator.next())) {
iterator.remove();
return true;
}
return false;
}
/**
* @return true if this {@code Sequence} contains all of the given items, false otherwise.
*
* @since 2.2
*/
default boolean containsAll(Object... items) {
return Iterables.containsAll(this, items);
}
/**
* @return true if this {@code Sequence} contains all of the items in the given {@link Iterable}, false otherwise.
*
* @since 2.2
*/
default boolean containsAll(Iterable items) {
if (items instanceof Collection)
return containsAll((Collection) items);
for (Object item : items)
if (!contains(item))
return false;
return true;
}
/**
* @return true if this {@code Sequence} contains all of the items in the given {@link Collection}, false
* otherwise.
*/
@Override
default boolean containsAll(Collection c) {
for (Object o : c)
if (!contains(o))
return false;
return true;
}
/**
* @return true if this {@code Sequence} contains any of the given items, false otherwise.
*/
default boolean containsAny(Object... items) {
return Iterables.containsAny(this, items);
}
/**
* @return true if this {@code Sequence} contains any of the given items, false otherwise.
*/
default boolean containsAny(Iterable items) {
return Iterables.containsAny(this, items);
}
/**
* @return true if this {@code Sequence} contains any of the items in the given {@link Collection}, false
* otherwise.
*
* @since 2.2
*/
default boolean containsAny(Collection c) {
for (Object o : c)
if (contains(o))
return true;
return false;
}
/**
* Add all the items in the given array to this {@code Sequence}.
*
* @return true if any items were added to this {@code Sequence}.
*
* @since 2.2
*/
@SuppressWarnings("unchecked")
default boolean addAll(T... items) {
boolean modified = false;
for (T t : items)
modified |= add(t);
return modified;
}
/**
* Add all the items in the given {@link Iterable} to this {@code Sequence}.
*
* @return true if any items were added to this {@code Sequence}.
*
* @since 2.2
*/
default boolean addAll(Iterable iterable) {
boolean modified = false;
for (T t : iterable)
modified |= add(t);
return modified;
}
/**
* Add all the items in the given {@link Collection} to this {@link Collection}.
*
* @return true if any items were added to this {@link Collection}.
*
* @since 2.2
*/
@Override
default boolean addAll(Collection c) {
boolean modified = false;
for (T t : c)
modified |= add(t);
return modified;
}
/**
* Remove all of the given items that are present in this {@link Collection}.
*
* @return true if any items were removed from this {@link Collection}.
*
* @since 2.2
*/
default boolean removeAll(Object... items) {
return Iterables.removeAll(this, items);
}
/**
* Remove all the items in the given {@link Iterable} that are present in this {@link Collection}.
*
* @return true if any items were removed from this {@link Collection}.
*
* @since 2.2
*/
default boolean removeAll(Iterable items) {
return Iterables.removeAll(this, items);
}
/**
* Remove all the items in the given {@link Collection} that are present in this {@link Collection}.
*
* @return true if any items were removed from this {@link Collection}.
*/
@Override
default boolean removeAll(Collection c) {
boolean removed = false;
for (Iterator iterator = iterator(); iterator.hasNext(); ) {
if (c.contains(iterator.next())) {
iterator.remove();
removed = true;
}
}
return removed;
}
/**
* Remove all items in this {@link Collection} that are not among the given items.
*
* @return true if any items were removed from this {@link Collection}.
*
* @since 2.2
*/
default boolean retainAll(Object... items) {
return Iterables.retainAll(this, items);
}
/**
* Remove all items in this {@link Collection} that are not among the items in the given {@link Iterable}.
*
* @return true if any items were removed from this {@link Collection}.
*
* @since 2.2
*/
default boolean retainAll(Iterable items) {
return Iterables.retainAll(this, items);
}
/**
* Remove all items in this {@link Collection} that are not among the items in the given {@link Collection}.
*
* @return true if any items were removed from this {@link Collection}.
*/
@Override
default boolean retainAll(Collection c) {
return Iterables.retainAll(this, c);
}
/**
* Remove all items in this {@link Collection} that do not match the given {@link Predicate}.
*
* @return true if any items were removed from this {@link Collection}.
*/
default boolean retainIf(Predicate condition) {
boolean modified = false;
for (Iterator iterator = iterator(); iterator.hasNext(); ) {
if (!condition.test(iterator.next())) {
iterator.remove();
modified = true;
}
}
return modified;
}
@Override
default void clear() {
Iterables.clear(this);
}
@Override
default Spliterator spliterator() {
return Spliterators.spliteratorUnknownSize(iterator(), 0);
}
}