Reverse a string in java without using reverse function

Let’s learn to reverse a string in java without using reverse function.

Reverse a string in java without using reverse function

Here are ways to reverse a string without using reverse function. One using for loop, while loop, and recursion.

Here’s the program to reverse a string using for loop without using reverse method. for loop loops until condition for(int a = strInput.length(); a > 0; –a) is false.

import java.util.Scanner;
public class ReverseWithoutFunction 
{
   public static void main(String[] args) 
   {
      String strInput;
      Scanner sc = new Scanner(System.in);  
      System.out.print("Please enter a string: ");  
      strInput = sc.nextLine();
      System.out.print("After reversing string is: ");  
      for(int a = strInput.length(); a > 0; --a)  
      {
         System.out.print(strInput.charAt(a - 1));  
      }
      sc.close();
   }
}


Output:

Please enter a string: flowerbrackets
After reversing string is: stekcarbrewolf

Please enter a string: helloworld
After reversing string is: dlrowolleh


Let’s see program to reverse a string using recursion. Recursive function is one which calls itself.

import java.util.Scanner;
public class ReverseStringUsingRecursion 
{
   String reverseRecursive(String str)
   {
      if(str.length() == 0)
          return " ";
      return str.charAt(str.length() - 1) + reverseRecursive(str.substring(0, str.length() - 1));
   }
   public static void main(String[] args) 
   {
      ReverseUsingRecursion obj = new ReverseUsingRecursion();
      Scanner sc = new Scanner(System.in);
      System.out.println("Please enter a string: ");
      String strInput = sc.nextLine();    
      System.out.println("Reverse string using recursion: " + obj.reverseRecursive(strInput));
      sc.close();
   }
}


Output:

Please enter a string: helloworld
Reverse string using recursion: dlrowolleh

Please enter a string: java
Reverse string using recursion: avaj


Now let’s learn to reverse a string in java using while loop. while loop loops until s > 0 becomes false.

import java.util.Scanner;
public class ReverseWithoutFunction 
{
   public static void main(String[] args) 
   {
      String strInput;
      Scanner sc = new Scanner(System.in);  
      System.out.print("Please enter a string: ");  
      strInput = sc.nextLine();
      System.out.print("After reversing string is: ");  
      int s = strInput.length();   
      while(s > 0)
      {
         System.out.print(strInput.charAt(s - 1));  
         s--;  
      }
      sc.close();
   }
}


Output:

Please enter a string: corejava
After reversing string is: avajeroc


Also read – abstraction in java