Write a java program to validate string using Regular Expression

Write a java program to validate string using Regular Expression. Given a string (s) apply the following rules.

1. String should be only four characters long.
   2. First character can be an alphabet or digit.
   3. Second character must be uppercase ‘R’.
   4. Third character must be a number between 0-9.

If all the conditions are satisifed then print TRUE else print FALSE.

The return type is the boolean formed based on rules.

Input and Output Format:

Input consists of a string.

Output consists of TRUE or FALSE .

Refer sample output for formatting specifications.

Sample Input 1:
vR4u

Sample Output 1:
TRUE

Sample Input 2:
vRau

Sample Output 2:
FALSE

Sample Input 3:
vrau

Sample Output 3:
FALSE

java program to validate string using Regular Expression

package com.demo;
 
import java.util.*;
 
public class Main {
 
public static Scanner sc;
 
public static void main(String[] args) {
sc = new Scanner(System.in);
String n = sc.nextLine();
System.out.println(display(n));
}
 
public static String display(String s) {
String w = "FALSE";
if (s.length() == 4 && (Character.isDigit(s.charAt(0)) || Character.isAlphabetic(s.charAt(0)))
&& s.charAt(1) == 'R') {
if (Character.isDigit(s.charAt(2)))
w = "TRUE";
}
return w;
 
}
}