Java Stack pop() Method

The pop() method in Java, part of the java.util.Stack class, is used to remove the element at the top of the stack and return that element. This method is fundamental to the stack's LIFO (Last-In-First-Out) behavior.

Table of Contents

1. Introduction
2. pop() Method Syntax
3. Understanding pop()
4. Examples
   • Basic Usage
   • Using pop() in a Loop
5. Real-World Use Case
6. Conclusion

Introduction

The pop() method removes the object at the top of the stack and returns that object as the value of this function. It is an essential operation for stack-based structures, where the most recently added element is the first to be removed.

pop() Method Syntax

The syntax for the pop() method is as follows:

public E pop()

Parameters:

• This method does not take any parameters.

Returns:

• The element at the top of the stack.

Throws:

• EmptyStackException: If the stack is empty.

Understanding pop()

The pop() method follows the LIFO (Last-In-First-Out) principle. It removes and returns the top element of the stack. If the stack is empty, calling pop() will throw an EmptyStackException.

Examples

Basic Usage

To demonstrate the basic usage of pop(), we will create a Stack object, push some elements onto the stack, and then pop elements from the stack.

Example

import java.util.Stack;

public class PopExample {
    public static void main(String[] args) {
        Stack<String> stack = new Stack<>();

        // Push elements onto the stack
        stack.push("apple");
        stack.push("banana");
        stack.push("cherry");

        // Pop the top element
        String topElement = stack.pop();
        System.out.println("Popped element: " + topElement);

        // The stack after popping
        System.out.println("Stack after pop: " + stack);
    }
}

Output:

Popped element: cherry
Stack after pop: [apple, banana]

Using pop() in a Loop

This example shows how to use pop() in a loop to remove all elements from the stack.

Example

import java.util.Stack;

public class PopInLoopExample {
    public static void main(String[] args) {
        Stack<Integer> stack = new Stack<>();

        // Push elements onto the stack
        stack.push(1);
        stack.push(2);
        stack.push(3);

        // Pop elements from the stack until it is empty
        while (!stack.empty()) {
            System.out.println("Popped element: " + stack.pop());
        }

        // Check if the stack is empty
        System.out.println("Is the stack empty? " + stack.empty());
    }
}

Output:

Popped element: 3
Popped element: 2
Popped element: 1
Is the stack empty? true

Real-World Use Case

Browser History Navigation

In real-world applications, the pop() method can be used for browser history navigation, where the most recent page visited is the first to be removed from the history.

Example

import java.util.Stack;

public class BrowserHistory {
    public static void main(String[] args) {
        Stack<String> history = new Stack<>();

        // User visits pages
        history.push("Home");
        history.push("About");
        history.push("Contact");

        // User presses back button
        System.out.println("Going back from: " + history.pop()); // Contact
        System.out.println("Going back from: " + history.pop()); // About

        // Current page
        System.out.println("Current page: " + history.peek()); // Home
    }
}

Output:

Going back from: Contact
Going back from: About
Current page: Home

Conclusion

The Stack.pop() method is used to remove and return the element at the top of the stack. This method is fundamental to the stack's LIFO behavior, making it essential for many stack-based operations. By understanding and using this method, you can efficiently manage stack-based data structures in your Java applications. Always handle potential EmptyStackException when using pop() on an empty stack.