Validating Programming File formats using Regular Expressions

Given some programming file names, the task is to check if they are valid or not using regular expressions. A valid programming file name follows the below conditions:

• It can contain alphabets (UpperCase or LowerCase), and digits and may contain a hyphen.
• It should contain one dot only that will be used as a suffix to save the file.
• Avoid special characters such as ?, %, #, /, and ‘:‘ in the filename.
• Every file should be saved with the right suffix used for separate programming languages.
• Some of the correct responses of the programming file extension are:
  • .java
  • .py
  • .c 
  • .PHP 
  • .class 

Valid Programming file format: 

file_name.extension_of_programming_language

Examples:

Input: file_name.java
Output: True

Input: .PHP_file_name
Output: False
Explanation: The programming file extension is not valid.

Approach: The problem can be solved based on the following idea:

Create a regex pattern to validate the number as written below: 

regex= “^.*\.(java|py|c|PHP|cs|cake|cshtml|csx|cpp|cp|cc|cobol|cob|ccp|css|flux|fx| go|jsp|kt|ktm|kts|numpy|numpyw|numsc|pls|pck|pkb|pks|plbplsql|sql|perl|r|rd|rsx|sh|bash|st|cs |swift|vb|class)$“

Where,

• ^ : indicates the start of the file
• .*(dot-star): will match everything except a newline (\n).
• |(Alternation) :Acts like a boolean OR and Matches the expression before or after the |.
• \. (Escape character): matches a dot(.) character.
• *(Quantifier): matches 0 or more of the preceding token(x)Capturing group: Matches x and remembers the match. For example, /(Rahul)/ matches and remembers “Rahul” in “Rahul Chauhan”.
• $  : End of the string

Follow the below steps to implement the idea:

• Create regex expression for the programming file names.
• If the input string is empty, Therefore return false.
• Else, Use the Pattern class to compile the regex formed.
• Use the matcher function to check whether the UPI id is valid or not.
• If it is valid, return true. Otherwise, return false.

Below is the implementation of the above approach.

C++

// C++ program to validate the
// Programming language file format Regular
// Expression

#include <bits/stdc++.h>
#include <regex>
using namespace std;

// Function to validate the
// Programming language file format
string isValidProgrammingFileFormat(string str)
{
    // Regex to check valid
    // Programming language file format.
    const regex pattern(
        "^.*\.(java|py|c|PHP|cs|cake|cshtml|csx|cpp|cp|cc|"
        "cobol|cob|ccp|css|flux|fx| "
        "go|jsp|kt|ktm|kts|numpy|numpyw|numsc|pls|pck|pkb|"
        "pks|plbplsql|sql|perl|r|rd|rsx|sh|bash|st|cs "
        "|swift|vb|class)$");

    // If the string is empty return false
    if (str.empty()) {
        return "false";
    }

    // Return true if the str
    // matched the ReGex
    if (regex_match(str, pattern)) {
        return "true";
    }
    else {
        return "false";
    }
}

// Driver Code
int main()
{
    // Test Case 1:
    string str1 = "file_name.java";
    cout << isValidProgrammingFileFormat(str1) << endl;

    // Test Case 2:
    string str2 = "file_name01.py";
    cout << isValidProgrammingFileFormat(str2) << endl;

    // Test Case 3:
    string str3 = "Java123";
    cout << isValidProgrammingFileFormat(str3) << endl;

    // Test Case 4:
    string str4 = "file_name.class";
    cout << isValidProgrammingFileFormat(str4) << endl;

    // Test Case 5:
    string str5 = "file_name.css";
    cout << isValidProgrammingFileFormat(str5) << endl;

    // Test Case 6:
    string str6 = ".PHP_file_name";
    cout << isValidProgrammingFileFormat(str6) << endl;

    return 0;
}

Java

// Java program to validate the
// Programming language file format using
// Regular Expression

import java.io.*;
import java.util.regex.*;

class GFG {

    // Function to validate the
    // Programming language file format
    public static boolean
    isValidProgrammingFileFormat(String str)
    {

        // Regex to check valid Programming
        // language file format
        String regex
            = "^.*\\.(java|py|c|PHP|cs|cake|cshtml|csx|c|cpp|cp|cc|cobol|cob|ccp|css|flux|fx|go|jsp|kt|ktm|kts|numpy|numpyw|numsc|pls|pck|pkb|pks|plbplsql|sql|perl|r|rd|rsx|sh|bash|st|cs|swift|vb|class)$";

        // Compile the ReGex
        Pattern p = Pattern.compile(regex);

        // If the string is empty return false
        if (str == null) {
            return false;
        }

        // Pattern class contains matcher()
        // method to find matching between
        // given Programming language file
        // format using regular expression.
        Matcher m = p.matcher(str);

        // Return if the str
        // matched the ReGex
        return m.matches();
    }

    // Driver Code
    public static void main(String args[])
    {
        // Test Case 1:
        String str1 = "file_name.java";
        System.out.println(
            isValidProgrammingFileFormat(str1));

        // Test Case 2:
        String str2 = "file_name01.py";
        System.out.println(
            isValidProgrammingFileFormat(str2));

        // Test Case 3:
        String str3 = "Java123";
        System.out.println(
            isValidProgrammingFileFormat(str3));

        // Test Case 4:
        String str4 = "file_name.class";
        System.out.println(
            isValidProgrammingFileFormat(str4));

        // Test Case 5:
        String str5 = "file_name.css";
        System.out.println(
            isValidProgrammingFileFormat(str5));

        // Test Case 6:
        String str6 = ".PHP_file_name";
        System.out.println(
            isValidProgrammingFileFormat(str6));
    }
}

Python3

# Python3 program to validate
# Programming language file format using
# Regular Expression

import re


# Function to validate
# Programming language file format
def isValidProgrammingFileFormat(str):

    # Regex to check valid Programming language 
    # file format
    regex = "^.*\.(java|py|c|PHP|cs|cake|cshtml|csx|cpp|cp|cc|cobol|cob|ccp|css|flux|fx| go|jsp|kt|ktm|kts|numpy|numpyw|numsc|pls|pck|pkb|pks|plbplsql|sql|perl|r|rd|rsx|sh|bash|st|cs |swift|vb|class)$"

    # Compile the ReGex
    p = re.compile(regex)

    # If the string is empty
    # return false
    if (str == None):
        return "false"

    # Return if the string
    # matched the ReGex
    if(re.search(p, str)):
        return "true"
    else:
        return "false"


# Driver code
if __name__ == '__main__':
    
    # Test Case 1:
    str1 = "file_name.java"
    print(isValidProgrammingFileFormat(str1))
    
    # Test Case 2:
    str2 = "file_name01.py"
    print(isValidProgrammingFileFormat(str2))
    
    # Test Case 3:
    str3 = "Java123"
    print(isValidProgrammingFileFormat(str3))
    
    # Test Case 4:
    str4 = "file_name.class"
    print(isValidProgrammingFileFormat(str4))
    
    # Test Case 5:
    str5 = "file_name.css"
    print(isValidProgrammingFileFormat(str5))
    
    # Test Case 6:
    str6 = ".PHP_file_name"
    print(isValidProgrammingFileFormat(str6))

C#

// C# program to validate the
// Programming language file format using
// Regular Expression
using System;
using System.Text.RegularExpressions;

public class GFG
{

  // Function to validate the
  // Programming language file format
  public static bool isValidProgrammingFileFormat(String str)
  {

    // Regex to check valid
    // Programming language file format.
    var regex = new Regex("^.*\\.(java|py|c|PHP|cs|cake|cshtml|csx|c|cpp|cp|cc|cobol|cob|ccp|css|flux|fx|go|jsp|kt|ktm|kts|numpy|numpyw|numsc|pls|pck|pkb|pks|plbplsql|sql|perl|r|rd|rsx|sh|bash|st|cs|swift|vb|class)$");

    // If the string is empty return false
    if (str == null)
    {
      return false;
    }

    // Pattern class contains matcher()
    // method to find matching between
    // given Programming language file
    // format using regular expression.
    var m = regex.Match(str);

    // Return if the str
    // matched the ReGex
    return m.Success;
  }

  // Driver Code.
  public static void Main(String[] args)
  {
    // Test Case 1:
    var str1 = "file_name.java";
    Console.WriteLine(
      isValidProgrammingFileFormat(str1));

    // Test Case 2:
    var str2 = "file_name01.py";
    Console.WriteLine(
      isValidProgrammingFileFormat(str2));

    // Test Case 3:
    var str3 = "Java123";
    Console.WriteLine(
      isValidProgrammingFileFormat(str3));

    // Test Case 4:
    var str4 = "file_name.class";
    Console.WriteLine(
      isValidProgrammingFileFormat(str4));

    // Test Case 5:
    var str5 = "file_name.css";
    Console.WriteLine(
      isValidProgrammingFileFormat(str5));

    // Test Case 6:
    var str6 = ".PHP_file_name";
    Console.WriteLine(
      isValidProgrammingFileFormat(str6));

  }
}

// This code is contributed by Pushpesh Raj.

Javascript

// Javascript program to validate
// Programming language file format using Regular Expression

// Function to validate the
// Programming language file format
function isValidProgrammingFileFormat(str) {
    // Regex to check valid
    // Programming language file format
    let regex = new RegExp(/^.*\.(java|py|c|PHP|cs|cake|cshtml|csx|cpp|cp|cc|cobol|cob|ccp|css|flux|fx| go|jsp|kt|ktm|kts|numpy|numpyw|numsc|pls|pck|pkb|pks|plbplsql|sql|perl|r|rd|rsx|sh|bash|st|cs |swift|vb|class)$/);

    // if str
    // is empty return false
    if (str == null) {
        return "false";
    }

    // Return true if the str
    // matched the ReGex
    if (regex.test(str) == true) {
        return "true";
    }
    else {
        return "false";
    }
}

// Driver Code
// Test Case 1:
let str1 = "file_name.java";
console.log(isValidProgrammingFileFormat(str1));

// Test Case 2:
let str2 = "file_name01.py";
console.log(isValidProgrammingFileFormat(str2));

// Test Case 3:
let str3 = "Java123";
console.log(isValidProgrammingFileFormat(str3));

// Test Case 4:
let str4 = "file_name.class";
console.log(isValidProgrammingFileFormat(str4));

// Test Case 5:
let str5 = "file_name.css";
console.log(isValidProgrammingFileFormat(str5));

// Test Case 6:
let str6 = ".PHP_file_name";
console.log(isValidProgrammingFileFormat(str6));

Output

true
true
false
true
true
false

Time Complexity: O(N) for each test case, where N is the length of the given string. 
Auxiliary Space: O(1)