Reverse a String in Java

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Today we will learn about how to write a Java Program to Reverse a String in Java. Before moving forward, we must have knowledge about what is String Java?

What is String in Java?

The char type represents only one character. To represent a string of characters, use the data type called String. For example, the following code declares a message to be a string with the value "Welcome to TechWithCode".

String message = "Welcome to TechWithCode";

The string is a predefined class in the Java library, just like the classes System and Scanner.

The String type is not a primitive type. It is known as a reference type. Any Java class can be used as a reference type for a variable

The reverse of a String:

It refers that shifting the character of a string from left to right or vice-versa

Java Programm of Reverse of String:

There can be many ways to write a program to reverse a string in java but here we will see total four ways to write a java program to reverse a string.

1. Reverse a String in Java using CharAt Method

Problem Statement⤵️

Write a Java program to Reverse a String using CharAt Method.

Source code⤵️

import java.util.*;
public class StringReverse{
public static void main(String args[]) {
String inpt, rev="";
Scanner in=new Scanner(System.in);
System.out.println("Enter the string");
inpt=in.nextLine();
int length=inpt.length();
for(int i=length-1;i>=0;i--)
  rev=rev+inpt.charAt(i);
System.out.println("Reversed string: "+rev);
}
}

output⤵️

Enter the string
HELLO TECHWITHCODE
Reversed string: EDOCHTIWHCET OLLEH

2. Reverse a String in Java using String Builder / String Buffer Class

Problem Statement⤵️

Write a Java program to Reverse a String using String Builder / String Buffer Class.

Source code⤵️

import java.util.*; 
public class StringRev{
// Function to reverse a string in Java using StringBuilder
public static String rev(String s){
return new StringBuilder(s).reverse().toString();
}
public static void main(String[] args){
String s= "Welcome to TECHWITHCODE";
s= rev(s);
System.out.println("Result after reversing a string is : "+s);
}
}

output⤵️

Result after reversing a string is : ODOCHTIWHCET ot emocleW

3. String Reverse in java using Recursion

Problem Statement⤵️

Write a Java program to String Reverse using Recursion

Source code⤵️

import java.util.*;
public class StringRecursion{
String rev(String str) {
if(str.length() == 0)
return " ";
return str.charAt(str.length()-1) + rev(str.substring(0,str.length()-1)); }
public static void main(String[ ] args) {
StringRecursion r=new StringRecursion();
Scanner sc=new Scanner(System.in);
System.out.print("Enter the string : ");
String s=sc.nextLine();
System.out.println("Reversed String: "+r.rev(s)); }
}

output⤵️

Enter the string : TechWithCode is best CSE site
Reversed String: etis ESC si edoChtiWhceT

4. Reversing a String in java using Reverse Iteration

Problem Statement⤵️

Write a Java program to Reverse a String using Reverse Iteration.

Source code⤵️

import java.util.*;
public class StringRev{
// Function to reverse a string in Java 
public static String reverseString(String s){
//Converting the string into a character array
char c[]=s.toCharArray();
String reverse="";
//For loop to reverse a string
for(int i=c.length-1;i>=0;i--){
reverse+=c[i];
}
return reverse;
}
 
public static void main(String[] args) {
System.out.println(reverseString("Hi All"));
System.out.println(reverseString("Welcome to TechWithcode"));
}
}

output⤵️

llA iH
edoChtiWhceT ot emocleW