Reverse a String in Java Without Using Inbuilt Methods

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Reversing a string is a fundamental task in programming and a common interview question. While Java provides inbuilt methods like StringBuilder.reverse() or StringBuffer.reverse() to achieve this, let's explore how to reverse a string without using these methods. In this post, we'll walk through a simple and efficient method to reverse a string in Java.

The Approach

To reverse a string without using inbuilt methods, we'll convert the string to a character array, then swap the characters from both ends moving towards the center.

Example Code

Let's look at the Java code that implements this approach:

java
public class StringReversal {
    public static String reverseString(String input) {
        // Convert the string to a character array
        char[] charArray = input.toCharArray();

        int start = 0;
        int end = charArray.length - 1;

        // Swap characters from both ends
        while (start < end) {
            // Swap characters
            char temp = charArray[start];
            charArray[start] = charArray[end];
            charArray[end] = temp;

            // Move towards the center
            start++;
            end--;
        }

        // Convert the character array back to a string
        return new String(charArray);
    }

    public static void main(String[] args) {
        String inputString = "Hello, World!";
        String reversedString = reverseString(inputString);
        System.out.println("Original string: " + inputString);
        System.out.println("Reversed string: " + reversedString);
    }
}

In this example, we define a method reverseString that takes a string as input and reverses it using the approach mentioned above. We then demonstrate this by reversing a sample string.

Conclusion

Reversing a string is a fundamental programming skill. By understanding and implementing approaches like the one shown in this post, you'll not only be prepared for interviews but also strengthen your understanding of string manipulation in Java.

By writing efficient and clean code to reverse a string, you demonstrate your proficiency in the language. Keep practicing and exploring different string manipulation techniques to enhance your coding skills!