deque Comparison of Queue and Deque methods Comparison of Stack and Deque methods

1、

隊列queue和雙端隊列deque的轉換

Queue Method Equivalent Deque Method

add(e) addLast(e)

offer(e) offerLast(e)

remove() removeFirst()

poll() pollFirst()

element() getFirst()

peek() peekFirst()

2、

堆stack和deque的轉換

Stack Method Equivalent Deque Method

push(e) addFirst(e)

pop() removeFirst()

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Deque (Java Platform SE 8 ) https://docs.oracle.com/javase/8/docs/api/java/util/Deque.html

compact1, compact2, compact3

java.util

Type Parameters:

​<code>​E​</code>​ - the type of elements held in this collectionAll Superinterfaces:

​

​Collection​​&lt;E&gt;, ​​Iterable​​&lt;E&gt;, ​​Queue​​&lt;E&gt;All Known Subinterfaces:

​BlockingDeque​​&lt;E&gt;All Known Implementing Classes:

​ArrayDeque​​, ​​ConcurrentLinkedDeque​​, ​​LinkedBlockingDeque​​, ​​LinkedList​​

public interface Deque&lt;E&gt;extends

Queue&lt;E&gt;

A linear collection that supports element insertion and removal at both ends. The name deque is short for "double ended queue" and is usually pronounced "deck". Most <code>Deque</code> implementations place no fixed limits on the number of elements they may contain, but this interface supports capacity-restricted deques as well as those with no fixed size limit.

This interface defines methods to access the elements at both ends of the deque. Methods are provided to insert, remove, and examine the element. Each of these methods exists in two forms: one throws an exception if the operation fails, the other returns a special value (either <code>null</code> or <code>false</code>, depending on the operation). The latter form of the insert operation is designed specifically for use with capacity-restricted <code>Deque</code> implementations; in most implementations, insert operations cannot fail.

The twelve methods described above are summarized in the following table:

Summary of Deque methods

 First Element (Head)Last Element (Tail) Throws exceptionSpecial valueThrows exceptionSpecial valueInsertaddFirst(e)offerFirst(e)addLast(e)offerLast(e)RemoveremoveFirst()pollFirst()removeLast()pollLast()ExaminegetFirst()peekFirst()getLast()peekLast()

This interface extends the Queue interface. When a deque is used as a queue, FIFO (First-In-First-Out) behavior results. Elements are added at the end of the deque and removed from the beginning. The methods inherited from the <code>Queue</code> interface are precisely equivalent to <code>Deque</code> methods as indicated in the following table:

Comparison of Queue and Deque methods

<code>Queue</code> MethodEquivalent <code>Deque</code> Methodadd(e)addLast(e)offer(e)offerLast(e)remove()removeFirst()poll()pollFirst()element()getFirst()peek()peekFirst()

Deques can also be used as LIFO (Last-In-First-Out) stacks. This interface should be used in preference to the legacy Stack class. When a deque is used as a stack, elements are pushed and popped from the beginning of the deque. Stack methods are precisely equivalent to <code>Deque</code> methods as indicated in the table below:

Comparison of Stack and Deque methods

Stack MethodEquivalent <code>Deque</code> Methodpush(e)addFirst(e)pop()removeFirst()peek()peekFirst()

Note that the peek method works equally well when a deque is used as a queue or a stack; in either case, elements are drawn from the beginning of the deque.

This interface provides two methods to remove interior elements, removeFirstOccurrence and removeLastOccurrence.

Unlike the List interface, this interface does not provide support for indexed access to elements.

While <code>Deque</code> implementations are not strictly required to prohibit the insertion of null elements, they are strongly encouraged to do so. Users of any <code>Deque</code> implementations that do allow null elements are strongly encouraged not to take advantage of the ability to insert nulls. This is so because <code>null</code> is used as a special return value by various methods to indicated that the deque is empty.

<code>Deque</code> implementations generally do not define element-based versions of the <code>equals</code> and <code>hashCode</code> methods, but instead inherit the identity-based versions from class <code>Object</code>.

This interface is a member of the Java Collections Framework.

Since:

1.6