package java.util; /** *双向队列 *队头:可以插入可以删除 *队尾:可以插入可以删除 *继承Queue接口 * * @author Doug Lea * @author Josh Bloch * @since 1.6 * @param <E> the type of elements held in this collection */ public interface Deque<E> extends Queue<E> { /** * 插入一个元素到队列前面 * * @param 插入一个元素到队列前面 * @throws IllegalStateException 如果超出了容量限制就抛出异常 * @throws ClassCastException 如果指定元素的类阻止其加入队列抛出异常 * @throws NullPointerException 如果添加的元素为null,而该实现类不允许null加入,则抛出异常 * @throws IllegalArgumentException 如果一些其他的限制某些类型的数据加入其中,则抛出异常 */ void addFirst(E e); /** * 插入一个元素到队列后面 * * @param 插入一个元素到队列后面 * @throws IllegalStateException 如果超出了容量限制就抛出异常 * @throws ClassCastException 如果指定元素的类阻止其加入队列抛出异常 * @throws NullPointerException 如果添加的元素为null,而该实现类不允许null加入,则抛出异常 * @throws IllegalArgumentException 如果一些其他的限制某些类型的数据加入其中,则抛出异常 */ void addLast(E e); /** * 插入一个元素到队列前面,如果违反容量限制,就抛出异常 * @param 插入一个元素到队列前面 * @return 插入一个元素到队列前面,插入成功,还回true;插入失败,还回false * @throws ClassCastException 如果指定元素的类阻止其加入队列抛出异常 * @throws NullPointerException 如果添加的元素为null,而该实现类不允许null加入,则抛出异常 * @throws IllegalArgumentException 如果一些其他的限制某些类型的数据加入其中,则抛出异常 */ boolean offerFirst(E e); /** * 插入一个元素到队列后面,如果违反容量限制,就抛出异常 * @param 插入一个元素到队列后面 * @return 插入一个元素到队列后面,插入成功,还回true;插入失败,还回false * @throws ClassCastException 如果指定元素的类阻止其加入队列抛出异常 * @throws NullPointerException 如果添加的元素为null,而该实现类不允许null加入,则抛出异常 * @throws IllegalArgumentException 如果一些其他的限制某些类型的数据加入其中,则抛出异常 */ boolean offerLast(E e); /** *检索并删除此deque的第一个元素。 * * @return 还回第一个元素 * @throws NoSuchElementException 如果队列是空 */ E removeFirst(); /** *检索并删除此deque的最后一个元素。 * * @return 还回最后一个元素 * @throws NoSuchElementException 如果队列是空 */ E removeLast(); /** *检索并删除此deque的第一个元素。 * * @return 还回第一个元素,如果队列是空则还回null值 */ E pollFirst(); /** *检索并删除此deque的最后一个元素。 * * @return 还回最后一个元素,如果队列是空则还回null值 */ E pollLast(); /** * 检索并获得此deque的第一个元素。 * @return 还回第一个元素 * @throws NoSuchElementException 如果是空的队列就抛异常 */ E getFirst(); /** * 检索并获得此deque的最后一个元素。 * @return 还回最后一个元素 * @throws NoSuchElementException 如果是空的队列就抛异常 */ E getLast(); /** * 检索并获得此deque的第一个元素。 * @return 返回第一个元素, 或者如果是空的队列则返回null */ E peekFirst(); /** * 检索并获得此deque的最后一个元素。 * @return 返回最后一个元素, 或者如果是空的队列则返回null */ E peekLast(); /** * 从此deque中删除指定元素的第一个出现。 * * @return 从此deque中删除指定元素的第一个出现,成功就返回true * @throws ClassCastException 如果指定元素的类与此队列不相容 * @throws NullPointerException 如果该元素为null且不允许为null */ boolean removeFirstOccurrence(Object o); /** * 从此deque中删除指定元素的最后一个出现。 * * @return 从此deque中删除指定元素的最后一个出现,成功就返回true * @throws ClassCastException 如果指定元素的类与此队列不相容 * @throws NullPointerException 如果该元素为null且不允许为null */ boolean removeLastOccurrence(Object o); // Queue methods (队列的方法) /** * Inserts the specified element into the queue represented by this deque * (in other words, at the tail of this deque) if it is possible to do so * immediately without violating capacity restrictions, returning * {@code true} upon success and throwing an * {@code IllegalStateException} if no space is currently available. * When using a capacity-restricted deque, it is generally preferable to * use {@link #offer(Object) offer}. * * <p>This method is equivalent to {@link #addLast}. * * @param e the element to add * @return {@code true} (as specified by {@link Collection#add}) * @throws IllegalStateException if the element cannot be added at this * time due to capacity restrictions * @throws ClassCastException if the class of the specified element * prevents it from being added to this deque * @throws NullPointerException if the specified element is null and this * deque does not permit null elements * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this deque */ boolean add(E e); /** * Inserts the specified element into the queue represented by this deque * (in other words, at the tail of this deque) if it is possible to do so * immediately without violating capacity restrictions, returning * {@code true} upon success and {@code false} if no space is currently * available. When using a capacity-restricted deque, this method is * generally preferable to the {@link #add} method, which can fail to * insert an element only by throwing an exception. * * <p>This method is equivalent to {@link #offerLast}. * * @param e the element to add * @return {@code true} if the element was added to this deque, else * {@code false} * @throws ClassCastException if the class of the specified element * prevents it from being added to this deque * @throws NullPointerException if the specified element is null and this * deque does not permit null elements * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this deque */ boolean offer(E e); /** * Retrieves and removes the head of the queue represented by this deque * (in other words, the first element of this deque). * This method differs from {@link #poll poll} only in that it throws an * exception if this deque is empty. * * <p>This method is equivalent to {@link #removeFirst()}. * * @return the head of the queue represented by this deque * @throws NoSuchElementException if this deque is empty */ E remove(); /** * Retrieves and removes the head of the queue represented by this deque * (in other words, the first element of this deque), or returns * {@code null} if this deque is empty. * * <p>This method is equivalent to {@link #pollFirst()}. * * @return the first element of this deque, or {@code null} if * this deque is empty */ E poll(); /** * Retrieves, but does not remove, the head of the queue represented by * this deque (in other words, the first element of this deque). * This method differs from {@link #peek peek} only in that it throws an * exception if this deque is empty. * * <p>This method is equivalent to {@link #getFirst()}. * * @return the head of the queue represented by this deque * @throws NoSuchElementException if this deque is empty */ E element(); /** * Retrieves, but does not remove, the head of the queue represented by * this deque (in other words, the first element of this deque), or * returns {@code null} if this deque is empty. * * <p>This method is equivalent to {@link #peekFirst()}. * * @return the head of the queue represented by this deque, or * {@code null} if this deque is empty */ E peek(); // *** Stack methods *** /** * Pushes an element onto the stack represented by this deque (in other * words, at the head of this deque) if it is possible to do so * immediately without violating capacity restrictions, throwing an * {@code IllegalStateException} if no space is currently available. * * <p>This method is equivalent to {@link #addFirst}. * * @param e the element to push * @throws IllegalStateException if the element cannot be added at this * time due to capacity restrictions * @throws ClassCastException if the class of the specified element * prevents it from being added to this deque * @throws NullPointerException if the specified element is null and this * deque does not permit null elements * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this deque */ void push(E e); /** * Pops an element from the stack represented by this deque. In other * words, removes and returns the first element of this deque. * * <p>This method is equivalent to {@link #removeFirst()}. * * @return the element at the front of this deque (which is the top * of the stack represented by this deque) * @throws NoSuchElementException if this deque is empty */ E pop(); // *** Collection methods *** /** * Removes the first occurrence of the specified element from this deque. * If the deque does not contain the element, it is unchanged. * More formally, removes the first element {@code e} such that * <tt>(o==null ? e==null : o.equals(e))</tt> * (if such an element exists). * Returns {@code true} if this deque contained the specified element * (or equivalently, if this deque changed as a result of the call). * * <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. * * @param o element to be removed from this deque, if present * @return {@code true} if an element was removed as a result of this call * @throws ClassCastException if the class of the specified element * is incompatible with this deque * (<a href="Collection.html#optional-restrictions">optional</a>) * @throws NullPointerException if the specified element is null and this * deque does not permit null elements * (<a href="Collection.html#optional-restrictions">optional</a>) */ boolean remove(Object o); /** * Returns {@code true} if this deque contains the specified element. * More formally, returns {@code true} if and only if this deque contains * at least one element {@code e} such that * <tt>(o==null ? e==null : o.equals(e))</tt>. * * @param o element whose presence in this deque is to be tested * @return {@code true} if this deque contains the specified element * @throws ClassCastException if the type of the specified element * is incompatible with this deque * (<a href="Collection.html#optional-restrictions">optional</a>) * @throws NullPointerException if the specified element is null and this * deque does not permit null elements * (<a href="Collection.html#optional-restrictions">optional</a>) */ boolean contains(Object o); /** * Returns the number of elements in this deque. * * @return the number of elements in this deque */ public int size(); /** * Returns an iterator over the elements in this deque in proper sequence. * The elements will be returned in order from first (head) to last (tail). * * @return an iterator over the elements in this deque in proper sequence */ Iterator<E> iterator(); /** * Returns an iterator over the elements in this deque in reverse * sequential order. The elements will be returned in order from * last (tail) to first (head). * * @return an iterator over the elements in this deque in reverse * sequence */ Iterator<E> descendingIterator(); }
Java 集合系列(12): Deque接口源码
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