Java中的LinkedList pop()方法

Java.util.LinkedList.pop() 方法用于从LinkedList 表示的堆栈中移除并返回顶部元素。该方法只是弹出堆栈顶部的元素。该方法类似于 LinkedList 中的 removeFirst 方法。

语法：

LinkedListObject.pop()

参数：该方法不带任何参数。

返回值：该方法返回由 LinkedList 表示的堆栈的第一个（堆栈顶部）值。

异常：如果 LinkedList 表示的堆栈中没有元素，pop 方法将抛出NoSuchElementException() 。

下面的程序说明了Java.util.LinkedList.pop() 方法：
方案一：

// Java code to demonstrate pop method in LinkedList
  
import java.util.LinkedList;
  
public class GfG {
    // Main method
    public static void main(String[] args)
    {
  
        // Creating a LinkedList object to represent a stack.
        LinkedList stack = new LinkedList<>();
  
        // Pushing an element in the stack
        stack.push("Geeks");
  
        // Pushing an element in the stack
        stack.push("for");
  
        // Pop an element from stack
        String s = stack.pop();
  
        // Printing the popped element.
        System.out.println(s);
  
        // Pushing an element in the stack
        stack.push("Geeks");
  
        // Printing the complete stack.
        System.out.println(stack);
    }
}

输出：

for
[Geeks, Geeks]

方案二：

// Java code to demonstrate pop method in LinkedList
  
import java.util.LinkedList;
  
public class GfG {
    // Main method
    public static void main(String[] args)
    {
  
        // Creating a LinkedList object to represent a stack.
        LinkedList stack = new LinkedList<>();
  
        // Pushing an element in the stack
        stack.push(10);
  
        // Pushing an element in the stack
        stack.push(20);
  
        // Pop an element from stack
        Integer ele = stack.pop();
  
        // Printing the popped element.
        System.out.println(ele);
  
        // Pop an element from stack
        ele = stack.pop();
  
        // Printing the popped element.
        System.out.println(ele);
  
        // Throws NoSuchElementException
        ele = stack.pop();
  
        // Throwsca runtime exception
        System.out.println(ele);
  
        // Printing the complete stack.
        System.out.println(stack);
    }
}

输出：

20
10

then it will throw :
Exception in thread "main" java.util.NoSuchElementException
    at java.util.LinkedList.removeFirst(LinkedList.java:270)
    at java.util.LinkedList.pop(LinkedList.java:801)
    at GfG.main(GfG.java:35)