We need to write a java program to reverse string and output it. Here, string can be a single word or a sentence.
Example:
1 2 3 4 5 | Input: Pencil Output: licneP Input: Java Program Output: margorP avaJ |
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
- Take input a string (str).
- Loop (i) through (str) from back to front.
- Concatenate the character at position (i) of (str) to (rev).
- Output (rev).
Reverse String in Java using For Loop
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | 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
1 2 3 | Enter a String pencil programmer Reversed String: remmargorp licnep |
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.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | 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
1 2 3 | Enter a String Reversing a sting Reversed String: gnits a gnisreveR |
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.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | 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
1 2 3 | Enter a String Dhoni Reversed String: inohD |
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.