JavaRegex.java

/*
Java Regex

Write a class called myRegex which will contain a string pattern. You need to write a regular expression and assign it to 
the pattern such that it can be used to validate an IP address. Use the following definition of an IP address:

IP address is a string in the form "A.B.C.D", where the value of A, B, C, and D may range from 0 to 255. Leading zeros are 
allowed. The length of A, B, C, or D can't be greater than 3.
Some valid IP address:

000.12.12.034
121.234.12.12
23.45.12.56
Some invalid IP address:

000.12.234.23.23
666.666.23.23
.213.123.23.32
23.45.22.32.
I.Am.not.an.ip
In this problem you will be provided strings containing any combination of ASCII characters. You have to write a regular 
expression to find the valid IPs.

Just write the myRegex class, and we will append your code after the following piece of code automatically before running it:

*/

import java.util.Scanner;

class Solution {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            String IP = in.next();
            boolean isValid = IP.matches(new MyRegex().pattern);
            System.out.println(isValid);
        }
    }
}

class MyRegex {
    String num = "([01]?\\d{1,2}|2[0-4]\\d|25[0-5])";

    // Construct the pattern using the defined numeric segment
    String pattern = num + "." + num + "." + num + "." + num;
}