How to check if a string is a valid URL in Kotlin

How to check if a string is a valid URL in Kotlin.

Here's a step-by-step tutorial on how to check if a string is a valid URL in Kotlin:

1. Import the necessary classes:

   import java.net.URL
   import java.net.MalformedURLException

2. Create a function that takes a string parameter for the URL and returns a boolean indicating whether it is valid or not:

   fun isValidUrl(urlString: String): Boolean {
       try {
           URL(urlString)
           return true
       } catch (e: MalformedURLException) {
           return false
       }
   }

3. Call the isValidUrl function and pass the URL string as an argument to check if it is valid:

   val url = "https://www.example.com"
   val isValid = isValidUrl(url)
   println("Is $url a valid URL? $isValid")

4. The URL constructor will throw a MalformedURLException if the URL string is not valid. So, we catch that exception and return false if it occurs.

5. Here are a few additional examples to demonstrate the usage of the isValidUrl function:

   val url1 = "https://www.example.com"
   val isValid1 = isValidUrl(url1)
   println("Is $url1 a valid URL? $isValid1")
   
   val url2 = "ftp://ftp.example.com"
   val isValid2 = isValidUrl(url2)
   println("Is $url2 a valid URL? $isValid2")
   
   val url3 = "invalid-url"
   val isValid3 = isValidUrl(url3)
   println("Is $url3 a valid URL? $isValid3")

   Output:

   Is https://www.example.com a valid URL? true
   Is ftp://ftp.example.com a valid URL? true
   Is invalid-url a valid URL? false

By following these steps, you can easily check if a string is a valid URL in Kotlin.