Java program to reverse a string

Hi all , Today I am going to write a post on very popular interview program which is How to Reverse a string in Java .

As String interview question have always been a favorite of almost all interviewers there’s always been a program on String manipulation in an interview .String programs vary from searching a particular word  in a sentence or a file ,reverse a string ,Number of times a particular word or character appears in a sentence or file and many more .

So today I am going to discus how to reverse a String in java .This program also helps to find that whether a String is Palindrome or not .

A palindrome String can be checked by comparing the original String with the reverse of that String with the help of  equals() method or “==” .If both are equal then that means the String is palindrome .But for that first you need to know about how to reverse a String .

The reverse of a String example I have done it in two ways.

1. Reverse of String without using reverse method or Reverse a String using CharAt() method or Reverse a String without using String Buffer .
2. Reverse of String using reverse method or Reverse a String without using String Buffer .

If you know both of the methods to reverse a String then you can impress the interviewer by writing both the methods J

So , Here is the Example of  Reverse of String without using reverse method  or Reverse a String using CharAt() method or Reverse a String without using String Buffer .

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import java.util.*; class ReverseString {    public static void main(String args[])    {       String original, reverse = "";       Scanner in = new Scanner(System.in);         System.out.println("Enter a string to reverse");       original = in.nextLine();         int length = original.length();         for ( int i = length - 1 ; i >= 0 ; i-- )          reverse = reverse + original.charAt(i);         System.out.println("Reverse of entered string is: "+reverse);    } }

Explanation:

1. In the above Example we are asking the user to enter a String to reverse.

2. After calculating the length of the String we are using a loop to get each character from end of String ( as we are starting the loop form end) and then appending the characters using + operator .

This is quite simple example .Hope you all understand.

Now Comes the second method of Revere a String.

Reverse of String using reverse method or Reverse a String without using String Buffer .

import java.util.*; class InvertString {    public static void main(String args[])    {       StringBuffer a = new StringBuffer("Java programming is fun");       System.out.println(a.reverse());    } }

In this example we are using StringBuffer and its reverse method to reverse a string .

If you want input from user in StringBuffer case then you can use the program below :

import java.util.*; class ReverseString {    public static void main(String args[])    {       String original ;       Scanner in = new Scanner(System.in);         System.out.println("Enter a string to reverse");       original = in.nextLine();               StringBuffer a = new StringBuffer(original);       System.out.println(a.reverse());      } }

So this was my post on How to Reverse a String in Java .If you have any doubt or you know another efficient method please do write me .If you like this post please comment below  :)

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