Java StringBuilder reverse() example

In this guide, you will learn about the StringBuilder reverse() method in Java programming and how to use it with an example.

1. StringBuilder reverse() Method Overview


The reverse() method of the StringBuilder class is used to reverse the contents of the sequence, making it possible to easily invert the characters in a string.


- `stringBuilder.reverse()`


- The method doesn't take any parameters.

Key Points:

- After executing the reverse() method, the first character of the original sequence becomes the last in the modified sequence, the second becomes the second last, and so on.

- This method is particularly useful when you need to find a reversed version of a string, like in palindrome checking algorithms.

- Since StringBuilder is mutable, this operation modifies the content of the StringBuilder object without creating a new instance. This makes the operation faster and more memory efficient compared to string concatenations.

2. StringBuilder reverse() Method Example

public class StringBuilderReverseExample {
    public static void main(String[] args) {
        StringBuilder builder = new StringBuilder("Java is fun!");

        // Reversing the StringBuilder content
        System.out.println(builder); // Outputs: !nuf si avaJ

        // Using reversed string in a real-world example: palindrome check
        StringBuilder palindromeCandidate = new StringBuilder("level");
        StringBuilder original = new StringBuilder(palindromeCandidate);

        if (original.toString().equals(palindromeCandidate.toString())) {
            System.out.println(original + " is a palindrome.");
        } else {
            System.out.println(original + " is not a palindrome.");


!nuf si avaJ
level is a palindrome.


In this example:

1. We start with a StringBuilder object containing the string "Java is fun!".

2. By using the reverse() method, we modify the content of the StringBuilder to its reversed version, which is "!nuf si avaJ".

3. Next, we demonstrate a real-world use-case where the reverse() method can be handy. We check if a string is a palindrome by comparing it with its reversed version. In our case, "level" is indeed a palindrome.

The reverse() method in StringBuilder allows for quick in-place reversal of strings, enhancing performance and offering utility in various string manipulation scenarios.

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