Java Program to Reverse a String using Stack

A Stack is a linear data structure that follows the LIFO (Last In, First Out) principle. This property makes a stack useful for reversing a string because the last character inserted into the stack is the first character removed.

Stack follows the LIFO principle.
Each character is pushed into the stack.
Characters are popped in reverse order.

Example

Input: GeeksForGeeks
Output: skeeGroFskeeG

Approach

Create a Stack<Character> to store the characters of the string.
Traverse the string and push each character into the stack.
Pop characters from the stack until it becomes empty.
Store each popped character in a character array.
Convert the character array into a String and return it.

Java

import java.util.Stack;

public class GFG {

    // Method to reverse a string using Stack
    static String reverseString(String str) {

        Stack<Character> stack = new Stack<>();

        // Push each character into the stack
        for (int i = 0; i < str.length(); i++) {
            stack.push(str.charAt(i));
        }

        // Store the reversed characters
        char[] reversed = new char[str.length()];
        int i = 0;

        // Pop characters from the stack
        while (!stack.isEmpty()) {
            reversed[i++] = stack.pop();
        }

        return new String(reversed);
    }

    public static void main(String[] args) {

        String str1 = "GeeksForGeeks";
        String str2 = "Hello World";

        System.out.println("Original: " + str1);
        System.out.println("Reversed: " + reverseString(str1));

        System.out.println("Original: " + str2);
        System.out.println("Reversed: " + reverseString(str2));
    }
}

Output

Original: GeeksForGeeks
Reversed: skeeGroFskeeG
Original: Hello World
Reversed: dlroW olleH

Explanation

Create a Stack<Character> to store the string characters.
Push each character into the stack.
Pop characters one by one to get them in reverse order.
Store the popped characters in a character array.
Convert the array into a String and return it.

Java Program to Reverse a String using Stack

Example

Approach

Explore