Reverse a string using recursion in Java

Carvia Tech | November 21, 2020 | 1 min read | 105 views | Java Coding Challenges


In this article, we will write a program to reverse character positions in a given string using recursive approach.

Sample input
carvia
Reversed output
aivrca

Recursive Approach

  1. We will remove first character from the input string and append it at the end.

  2. Repeat it till all the characters are removed and input becomes empty.

Java source

Reverse a string using Recusion Java
public class ReverseString {

    public String reverse(String input) {
        if (input.isEmpty()) {  (1)
            System.out.println("String is empty now");
            return input;
        }
        return reverse(input.substring(1)) + input.charAt(0);   (2)
    }
}
1 Base condition in recursion
2 Tail recursion

JUnit testcase

We will write a simple Junit based testcase to assert the correctness of our given program.

JUnit Test
import org.junit.Test;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.*;

public class ReverseStringTest {

    @Test
    public void reverse() {
        ReverseString utils = new ReverseString();
        assertThat(utils.reverse("carvia"), equalTo("aivrac"));
    }
}

That’s all.


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