Java 中的 LinkedList pop()方法
原文:https://www . geesforgeks . org/linked list-pop-method-in-Java/
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一个元素。该方法类似于 LinkedList 中的 removeFirst 方法。
语法:
LinkedListObject.pop()
参数:该方法不取任何参数。
返回值:该方法返回 LinkedList 表示的栈的第一个(栈顶)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: 程序 1:
// 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<String> 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);
}
}
Output:
for
[Geeks, Geeks]
程序 2 :
// 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<Integer> 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)
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