Write a java program to reverse a String.

The provided Java program reverses a string entered by the user. Let's break down the logic step by step:

Steps of the Program

1. Importing the Scanner Class:

   ```java

   import java.util.Scanner;

   ```

   This line imports the `Scanner` class, which is used to read input from the console.

2. Class Definition:

   ```java

   public class ReverseString {

   ```

   This line defines a public class named `ReverseString`.

3. Main Method:

   ```java

   public static void main(String[] args) {

   ```

   This is the entry point of the program. The `main` method is where the program execution begins.

4. Creating a Scanner Object:

   Scanner scanner = new Scanner(System.in);

   This line creates a `Scanner` object to read input from the standard input stream (usually the keyboard).

5. Prompting the User for Input:

   System.out.print("Enter a string: ");

   This line prints a prompt asking the user to enter a string.

6. Reading the User Input:

   String str = scanner.nextLine();

   This line reads a full line of input from the user and stores it in the variable `str`.

7. Closing the Scanner:

   scanner.close();

   This line closes the `Scanner` object to prevent resource leaks.

8. Reversing the String:

   String reversedStr = new StringBuilder(str).reverse().toString();

   This line performs the actual string reversal:

   - `new StringBuilder(str)`: Creates a new `StringBuilder` object initialized with the string `str`.

   - `.reverse()`: Calls the `reverse` method on the `StringBuilder` object, which reverses the sequence of characters.

   - `.toString()`: Converts the reversed `StringBuilder` object back to a `String`.

9. Printing the Reversed String:

   System.out.println("Reversed String: " + reversedStr);

   This line prints the reversed string to the console.

Logic Breakdown

1. Input Handling: The program uses the `Scanner` class to read a string input from the user.

2. String Reversal:

   - StringBuilder: The `StringBuilder` class is used because it has a built-in method `reverse()` that efficiently reverses the sequence of characters in the `StringBuilder` object.

   - Conversion: The reversed sequence is converted back to a string using `toString()`.

3. Output: The reversed string is printed to the console.

Why Use StringBuilder?

- Efficiency: `StringBuilder` is mutable, meaning it can be modified without creating a new object for each modification. This makes it more efficient for operations like reversing a string, which involves multiple character manipulations.

- Convenience: The `StringBuilder` class provides a `reverse()` method that simplifies the reversal process compared to manually iterating through the string's characters and constructing the reversed string.

By utilizing `StringBuilder`, the code is both concise and efficient, making it a good choice for this task.

Complete java code: 

 import java.util.Scanner;

public class ReverseString {

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);

        System.out.print("Enter a string: ");

        String str = scanner.nextLine();

        scanner.close();

        

        String reversedStr = new StringBuilder(str).reverse().toString();

        System.out.println("Reversed String: " + reversedStr);

    }

}