Java Deque pollFirst() 方法

2025 年 3 月 22 日 | 阅读需 2 分钟

Java Deque 接口的 pollFirst() 方法用于检索并移除 deque 的第一个元素。如果给定的 deque 为空，该方法可能返回 null。

语法

参数

不适用

上述方法用于返回 deque 的头部。另一方面，如果 deque 为空，该方法可能会返回 null。

示例 1

import java.util.ArrayDeque;
import java.util.Deque;
public class JavaDequepollFirstExample1 {
   public static void main(String[] args) {
	   Deque<Character> deque = new ArrayDeque<>();
		deque.offer('q');
		deque.offer('u');
		deque.offer('e');
		deque.offer('r');
		deque.offer('y');
		Character val = deque.pollFirst();			
	System.out.println("The first character is given as : "+val);
	System.out.println("The remaining deque is : ");
		for (Character character : deque) {
			System.out.println(character);
		}   	
	}
}

输出

The first character is given as : q
The remaining deque is : 
u
e
r
y

示例 2

import java.util.ArrayDeque;
import java.util.Deque;
public class JavaDequepollFirstExample2 {
   public static void main(String[] args) {
	   Deque<String> deque = new ArrayDeque<>();
		deque.offer("Hello");
		deque.offer(" ");
		deque.offer("World");
		String val = deque.pollFirst();
		System.out.println("The first string is given as : "+val);
		System.out.println("The remaining deque is : "+deque);
	}
}

输出

The first string is given as : Hello
The remaining deque is : [ , World]

示例 3

import java.util.ArrayDeque;
import java.util.Deque;
public class JavaDequepollFirstExample3 {
   public static void main(String[] args) {
	 Deque<Long> deque = new ArrayDeque<>();
	    deque.offer(88l);
	    deque.offer(78l);
	    deque.offer(67l);
	   Long val = deque.peek();
	System.out.println("The first long value is given as : "+val);
	System.out.println("The resultant deque is : "+deque);  
   }

输出

The first long value is given as : 88
The resultant deque is : [88, 78, 67]

下一主题Java Deque

Java Deque pollFirst() 方法

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Java Deque pollFirst() 方法

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