Write a program to reverse a string using recursion in Java

Carvia Tech | May 18, 2019 | 1 min read | 241 views | Java Coding Challenges


In this article, we will write a program to reverse a string entered by a user.

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

JUnit testcase

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"));
    }
}

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