How to reverse String in Java

Reverse String in Java

Hi this is the frequent question that I faced in some of the interviews. So I choose this one to write as my first post.

We can reverse a String using StringBuffer or StringBuilder or without using these two by iteratively or recursively.

First we will see how to reverse a String using StringBuffer and StringBuilder reverse() method.

package com.interviewCodes.String;

public class ReverseStringDemo1 {

       public static void main(String[] args) {

      String orgStr = "Hello World";

      System.out.println("Original String : " + orgStr );

       // reverse a String using StringBuffer

       String revStr = new StringBuffer(orgStr).reverse().toString();

       System.out.println("Reversed String "+ revStr);

       // reverse a String using StringBuilder

       revStr = new StringBuilder(orgStr).reverse().toString();

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

       }

}

Now we  will how to reverse a String without using StringBuffer and StringBuilder by iteratively or recursively.

package com.interviewCodes.String;

public class ReverseStringDemo2 {

       public static void main(String[] args) {

             String orgnStr = "Hello World";

             System.out.println("Original String : " + orgnStr );

             //reverse a String iteratively

             String revStr = reverse(orgnStr);

             System.out.println("Reversed String "+ revStr);

             //reverse a String recursively

             revStr = reverseRecursively(orgnStr);

             System.out.println("Reversed String "+ revStr);

       } 

       // iterative method to reverse a String

       public static String reverse(String str) {

              if (str == null || str.isEmpty()) {

                     return str;

              }

              String reverse = "";

              for (int i = str.length() - 1; i >= 0; i--) {

                     reverse = reverse + str.charAt(i);

              }

              return reverse;

       }

       // reverse a String recursivly

       public static String reverseRecursively(String str) {

              if (str == null || str.isEmpty() || str.length() < 2) {

                     return str;

              }

              return reverseRecursively(str.substring(1)) + str.charAt(0);

       }

}
     

But I prefered to use StringBuffer or StringBuilder libraries to reverse a String.Please suggest if there are another ways of reversing a String.Thanks for reading.