JavaRegex.java

// 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 which contains a String "pattern". The string should contain the correct regular expression.

//(MyRegex class MUST NOT be public)

//Sample Input
//000.12.12.034
//121.234.12.12
//23.45.12.56
//00.12.123.123123.123
//122.23
//Hello.IP

//Sample Output
//true
//true
//true
//false
//false
//false




import java.util.regex.Matcher;
import java.util.regex.Pattern;
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();
            System.out.println(IP.matches(new MyRegex().pattern));
        }

    }
}
class MyRegex{

    protected static String pattern =  
"([0-9]|[0-9][0-9]|0[0-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])" 
+"\\."+"([0-9]|[0-9][0-9]|0[0-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])"
+"\\."+"([0-9]|[0-9][0-9]|0[0-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])"
+"\\."+"([0-9]|[0-9][0-9]|0[0-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])";

// Reference: https://www.regular-expressions.info/numericranges.html
// Reference: https://www.geeksforgeeks.org/how-to-validate-an-ip-address-using-regular-expressions-in-java/
}