Java Regex-HackerRank Solution

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
 

Solution

 

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

 

What is Regular Expression

A regular expression is a sequence of characters that forms a search pattern. When you search for data in a text, you can use this search pattern to describe what you are searching for.

A regular expression can be a single character or a more complicated pattern.

Regular expressions can be used to perform all types of text search and text replace operations.

Java does not have a built-in Regular Expression class, but we can import the java.util.regex package to work with regular expressions. The package includes the following classes:

•         Pattern Class - Defines a pattern (to be used in a search)
•         Matcher Class - Used to search for the pattern
•         PatternSyntaxException Class - Indicates syntax error in a regular expression pattern