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Vavr is an object-functional library for Java 8+
/* __ __ __ __ __ ___
* \ \ / / \ \ / / __/
* \ \/ / /\ \ \/ / /
* \____/__/ \__\____/__/
*
* Copyright 2014-2021 Vavr, http://vavr.io
*
* 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 io.vavr.collection;
import io.vavr.Tuple;
import io.vavr.Tuple2;
import io.vavr.control.Option;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.function.Consumer;
import java.util.function.Predicate;
/**
* @author Pap Lőrinc, Daniel Dietrich
*/
abstract class AbstractQueue> implements Traversable {
/**
* Removes an element from this Queue.
*
* @return a tuple containing the first element and the remaining elements of this Queue
* @throws NoSuchElementException if this Queue is empty
*/
public Tuple2 dequeue() {
if (isEmpty()) {
throw new NoSuchElementException("dequeue of empty " + getClass().getSimpleName());
} else {
return Tuple.of(head(), tail());
}
}
/**
* Removes an element from this Queue.
*
* @return {@code None} if this Queue is empty, otherwise {@code Some} {@code Tuple} containing the first element and the remaining elements of this Queue
*/
public Option> dequeueOption() {
return isEmpty() ? Option.none() : Option.some(dequeue());
}
/**
* Enqueues a new element.
*
* @param element The new element
* @return a new {@code Queue} instance, containing the new element
*/
public abstract Q enqueue(T element);
/**
* Enqueues the given elements. A queue has FIFO order, i.e. the first of the given elements is
* the first which will be retrieved.
*
* @param elements Elements, may be empty
* @return a new {@code Queue} instance, containing the new elements
* @throws NullPointerException if elements is null
*/
@SuppressWarnings("unchecked")
public Q enqueue(T... elements) {
Objects.requireNonNull(elements, "elements is null");
return enqueueAll(List.of(elements));
}
/**
* Enqueues the given elements. A queue has FIFO order, i.e. the first of the given elements is
* the first which will be retrieved.
*
* @param elements An Iterable of elements, may be empty
* @return a new {@code Queue} instance, containing the new elements
* @throws NullPointerException if elements is null
*/
public abstract Q enqueueAll(Iterable elements);
/**
* Returns the first element without modifying it.
*
* @return the first element
* @throws NoSuchElementException if this Queue is empty
*/
public T peek() {
if (isEmpty()) {
throw new NoSuchElementException("peek of empty " + getClass().getSimpleName());
} else {
return head();
}
}
/**
* Returns the first element without modifying the Queue.
*
* @return {@code None} if this Queue is empty, otherwise a {@code Some} containing the first element
*/
public Option peekOption() {
return isEmpty() ? Option.none() : Option.some(peek());
}
@Override
public Q dropUntil(Predicate predicate) {
Objects.requireNonNull(predicate, "predicate is null");
return dropWhile(predicate.negate());
}
@Override
public abstract Q dropWhile(Predicate predicate);
/**
* Dual of {@linkplain #tail()}, returning all elements except the last.
*
* @return a new instance containing all elements except the last.
* @throws UnsupportedOperationException if this is empty
*/
@Override
public abstract Q init();
/**
* Dual of {@linkplain #tailOption()}, returning all elements except the last as {@code Option}.
*
* @return {@code Some(Q)} or {@code None} if this is empty.
*/
@Override
public Option initOption() {
return isEmpty() ? Option.none() : Option.some(init());
}
/**
* Drops the first element of a non-empty Traversable.
*
* @return A new instance of Traversable containing all elements except the first.
* @throws UnsupportedOperationException if this is empty
*/
@Override
public abstract Q tail();
@Override
public Option tailOption() {
return isEmpty() ? Option.none() : Option.some(tail());
}
@Override
@SuppressWarnings("unchecked")
public Q retainAll(Iterable elements) {
return Collections.retainAll((Q) this, elements);
}
@SuppressWarnings("unchecked")
public Q removeAll(Iterable elements) {
return Collections.removeAll((Q) this, elements);
}
@Deprecated
public Q removeAll(Predicate predicate) {
Objects.requireNonNull(predicate, "predicate is null");
return reject(predicate);
}
@SuppressWarnings("unchecked")
@Override
public Q reject(Predicate predicate) {
return Collections.reject((Q) this, predicate);
}
@Override
public Q takeWhile(Predicate predicate) {
Objects.requireNonNull(predicate, "predicate is null");
return takeUntil(predicate.negate());
}
@Override
public abstract Q takeUntil(Predicate predicate);
@SuppressWarnings("unchecked")
@Override
public Q peek(Consumer action) {
Objects.requireNonNull(action, "action is null");
if (!isEmpty()) {
action.accept(head());
}
return (Q) this;
}
@Override
public String toString() {
return mkString(stringPrefix() + "(", ", ", ")");
}
}