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📜  Java Deque接口

📅  最后修改于: 2020-10-12 10:00:35             🧑  作者: Mango

Java Deque接口

Java Deque接口是一个线性集合，支持两端的元素插入和删除。 Deque是“双头队列”的缩写。

双端队列接口声明

public interface Deque extends Queue

Java Deque接口的方法

Method Description
boolean add(object) It is used to insert the specified element into this deque and return true upon success.
boolean offer(object) It is used to insert the specified element into this deque.
Object remove() It is used to retrieves and removes the head of this deque.
Object poll() It is used to retrieves and removes the head of this deque, or returns null if this deque is empty.
Object element() It is used to retrieves, but does not remove, the head of this deque.
Object peek() It is used to retrieves, but does not remove, the head of this deque, or returns null if this deque is empty.

ArrayDeque类

ArrayDeque类提供使用双端队列和可调整大小的数组的便利。它继承了AbstractCollection类并实现了Deque接口。

关于ArrayDeque类的要点是：

  • 与Queue不同，我们可以从两侧添加或删除元素。
  • ArrayDeque中不允许使用null元素。
  • 在没有外部同步的情况下，ArrayDeque不是线程安全的。
  • ArrayDeque没有容量限制。
  • ArrayDeque比LinkedList和Stack更快。

ArrayDeque层次结构

在页面右侧显示的图中给出了ArrayDeque类的层次结构。

ArrayDeque类声明

我们来看一下java.util.ArrayDeque类的声明。

public class ArrayDeque extends AbstractCollection implements Deque, Cloneable, Serializable

Java ArrayDeque示例

import java.util.*;
public class ArrayDequeExample {
   public static void main(String[] args) {
   //Creating Deque and adding elements
   Deque deque = new ArrayDeque();
   deque.add("Ravi");  
   deque.add("Vijay");   
   deque.add("Ajay");  
   //Traversing elements
   for (String str : deque) {
   System.out.println(str);
   }
   }
}

输出：

Ravi
Vijay
Ajay

Java ArrayDeque示例：offerFirst()和pollLast()

import java.util.*;
public class DequeExample {
public static void main(String[] args) {
Deque deque=new ArrayDeque();
deque.offer("arvind");
deque.offer("vimal");
deque.add("mukul");
deque.offerFirst("jai");
System.out.println("After offerFirst Traversal...");
for(String s:deque){
System.out.println(s);
}
//deque.poll();
//deque.pollFirst();//it is same as poll()
deque.pollLast();
System.out.println("After pollLast() Traversal...");
for(String s:deque){
System.out.println(s);
}
}
}

输出：

After offerFirst Traversal...
jai
arvind
vimal
mukul
After pollLast() Traversal...
jai
arvind
vimal

Java ArrayDeque示例：书

import java.util.*;  
class Book {  
int id;  
String name,author,publisher;  
int quantity;  
public Book(int id, String name, String author, String publisher, int quantity) {  
    this.id = id;  
    this.name = name;  
    this.author = author;  
    this.publisher = publisher;  
    this.quantity = quantity;  
}  
}  
public class ArrayDequeExample {  
public static void main(String[] args) {  
Deque set=new ArrayDeque();  
    //Creating Books  
    Book b1=new Book(101,"Let us C","Yashwant Kanetkar","BPB",8);  
    Book b2=new Book(102,"Data Communications & Networking","Forouzan","Mc Graw Hill",4);  
    Book b3=new Book(103,"Operating System","Galvin","Wiley",6);  
    //Adding Books to Deque 
    set.add(b1);  
    set.add(b2);  
    set.add(b3);  
    //Traversing ArrayDeque
    for(Book b:set){  
    System.out.println(b.id+" "+b.name+" "+b.author+" "+b.publisher+" "+b.quantity);  
    }  
}  
}

输出：

101 Let us C Yashwant Kanetkar BPB 8
102 Data Communications & Networking Forouzan Mc Graw Hill 4
103 Operating System Galvin Wiley 6