Java ArrayDeque addFirst()方法

java.util.ArrayDeque.addFirst(E e) 此方法将指定的元素插入此双端队列的前面。

1 语法

public void addFirst(E e)

2 参数

e：要在双端队列中添加的元素。

3 返回值

无

4 示例 

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * java.util.ArrayDeque.addFirst(E e)方法的例子
 */
import java.util.ArrayDeque;
import java.util.Deque;

public class Demo {
    public static void main(String[] args) {

        // create an empty array deque with an initial capacity
        Deque<Integer> deque = new ArrayDeque<Integer>(5);

        // use add() method to add elements in the deque
        deque.add(25);
        deque.add(30);
        deque.add(35);

        // use addFirst() method to add element at the front of the deque
        deque.addFirst(10);
        deque.addFirst(15);
        deque.addFirst(20);//now, element 20 will be at the front

        // these elments will be added in continuation with deque.add(35)
        deque.add(45);
        deque.add(40);

        // let us print all the elements available in deque
        for (Integer number : deque) {
            System.out.println("Number = " + number);
        }
    }
}

输出结果为：

Number = 20
Number = 15
Number = 10
Number = 25
Number = 30
Number = 35
Number = 45
Number = 40