Java Program to Reverse a String

We need to write a java program to reverse string and output it. Here, string can be a single word or a sentence.

Example:

A String in Java can be reversed in many ways. Let’s see each of the methods one by one.

Steps to Reverse a String in Java

  1. Take input a string (str).
  2. Loop (i) through (str) from back to front.
  3. Concatenate the character at position (i) of (str) to (rev).
  4. Output (rev).

Reverse String in Java using For Loop

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import java.util.Scanner;
 
public class StringReverse {
 
    public static void main(String args[]){
 
        Scanner in =new Scanner(System.in);
        String str, rev = "";
 
        //Input String
        System.out.println("Enter a String");
        str = in.nextLine();
 
        //Loop from back to front through 'str'
        for(int i=str.length()-1; i>=0; i--){
            rev = rev + str.charAt(i);
        }
 
        System.out.println("Reversed String: "+rev);
    }
}

Note: use nextLine() instead of next() to take sentence as input.

Output

Reverse String in Java using While Loop

In this method, we are using the same approach as the first java program but instead of for loop, we are using while loop. The loop starts from last index of the input string (i.e str.length()-1) and will end on 0.

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import java.util.Scanner;
 
public class ReverseString {
 
    public static void main(String args[]){
 
        Scanner in =new Scanner(System.in);
        String str, rev = "";
 
        //Input String
        System.out.println("Enter a String");
        str = in.nextLine();
 
        //last index of string
        int l = str.length()-1;
 
        //Loop from back to front through 'str'
        while(l >= 0){
            rev = rev + str.charAt(l--);
        }
 
        System.out.println("Reversed String: "+rev);
    }
}

Output

Reverse String in Java Without Loop

Java has StringBuilder class which has inbuilt reverse() method, which can reverse the string without any loops. For this we have to create StringBuilder object by passing input string as parameter.

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import java.util.Scanner;
 
public class ReverseStringWL {
 
    public static void main(String args[]){
 
        Scanner in =new Scanner(System.in);
        String str, rev = "";
 
        //Input String
        System.out.println("Enter a String");
        str = in.nextLine();
 
        StringBuilder sb = new StringBuilder(str);
 
        //Rerver using reverse() method
        rev =sb.reverse().toString();
 
        System.out.println("Reversed String: "+rev);
    }
}

Output

Choose whichever java program works best for you to reverse a string. If you like then share and if you have any doubts or suggestion then please comment below.

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