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Java Interview Question: Reverse a String (3 Easy Ways with Code)

 

🔹 Introduction

Reversing a string is one of the most commonly asked Java interview questions.
It helps interviewers test your understanding of strings and logic.

👉 In this article, we will learn 3 simple ways to reverse a string in Java.

🔹 Problem Statement

Given a string, reverse it.

Example:

Input: hello  
Output: olleh

🔹 Approach 1: Using StringBuilder (Easiest)

This is the simplest and most commonly used approach.

🔹 Java Code (StringBuilder)

public class ReverseString {
    public static void main(String[] args) {
        String str = "hello";

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

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

🔹 Approach 2: Using Loop (Manual Method)

This approach shows your logic-building skills.

🔹 Java Code (Using Loop)

public class ReverseString {
    public static void main(String[] args) {
        String str = "hello";
        String reversed = "";

        for (int i = str.length() - 1; i >= 0; i--) {
            reversed += str.charAt(i);
        }

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

🔹 Approach 3: Using Character Array

Efficient and clean approach.

🔹 Java Code (Char Array)

public class ReverseString {
    public static void main(String[] args) {
        String str = "hello";

        char[] arr = str.toCharArray();
        int left = 0;
        int right = arr.length - 1;

        while (left < right) {
            char temp = arr[left];
            arr[left] = arr[right];
            arr[right] = temp;

            left++;
            right--;
        }

        System.out.println("Reversed String: " + new String(arr));
    }
}

🔹 Time Complexity

  • O(n) for all approaches

🔹 Key Takeaways

✔ StringBuilder is easiest
✔ Loop method shows strong logic
✔ Char array approach is efficient

🔹 Conclusion

Reversing a string is a basic yet important Java interview question.
Make sure you understand all approaches to confidently answer in interviews.



🔗 Also Read

👉 First Non-Repeating Character in Java
👉 Check Palindrome String in Java

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