1. Introduction

Reversing a string is one of the classical problems in the field of computer science. One of the most efficient methods to achieve this is by using a stack. A stack is a Last In First Out (LIFO) data structure. In this post, we will use Java to reverse a string with the aid of a stack.

2. Program Steps

1. Create a Stack class with operations: push(), pop(), and isEmpty().

2. Push each character of the input string onto the stack.

3. Pop characters from the stack and construct the reversed string.

4. Display the reversed string.

3. Code Program

class Stack {
    private int maxSize;           // Size of the stack array
    private char[] stackArray;     // The stack array
    private int top;               // Index to the top element

    public Stack(int size) {
        this.maxSize = size;
        this.stackArray = new char[maxSize];
        this.top = -1;
    }

    // Push a character onto the top of the stack
    public void push(char ch) {
        if(top < maxSize - 1) {
            stackArray[++top] = ch;
        }
    }

    // Remove and return the top character from the stack
    public char pop() {
        return stackArray[top--];
    }

    // Check if the stack is empty
    public boolean isEmpty() {
        return (top == -1);
    }
}

public class ReverseStringUsingStack {
    public static void main(String[] args) {
        String input = "OpenAI";
        Stack stack = new Stack(input.length());

        // Push each character of the string onto the stack
        for (char ch : input.toCharArray()) {
            stack.push(ch);
        }

        String reversed = "";
        // Pop characters from the stack to get the reversed string
        while (!stack.isEmpty()) {
            reversed += stack.pop();
        }

        System.out.println("Original String: " + input);
        System.out.println("Reversed String: " + reversed);
    }
}

Output:

Original String: Master Coding
Reversed String: gnidoC retsaM

4. Step By Step Explanation

1. We first define a Stack class that is backed by a character array. This stack provides essential operations such as push, pop, and isEmpty.

2. We initiate the stack with a size equivalent to the length of the input string.

3. Each character of the input string is then pushed onto the stack.

4. As stacks follow a Last In First Out (LIFO) mechanism, popping characters from it inherently reverses the order. Thus, we construct our reversed string by popping characters from the stack until it's empty.

5. The result is a string that is the reverse of our input.

Using a stack for string reversal showcases the utility and efficiency of this data structure for such problems.