Understanding MalformedURLException in Java

What is MalformedURLException?

MalformedURLException is a subclass of IOException that signals that a malformed URL has occurred. This exception is thrown when a string that is supposed to represent a URL is not properly formatted.

When does MalformedURLException occur?

• Invalid URL Syntax: This exception occurs when a string passed to a URL constructor or a URL parsing method (like new URL(String spec) or URL.openConnection()) is not properly formatted according to the URL specification.
• Special Characters: MalformedURLException may occur if the URL string contains illegal characters or is missing required elements such as protocol identifier (like “http://”) or host name.
• Encoding Issues: If the URL contains characters that require encoding and they are not properly encoded, this exception can occur.

Handling MalformedURLException

To handle MalformedURLException, you can use try-catch blocks to catch the exception and handle it gracefully. Here’s how you can do it:

try {
    URL url = new URL("invalid_url_string");
} catch (MalformedURLException e) {
    System.out.println("Malformed URL Exception: " + e.getMessage());
    e.printStackTrace();
}

Examples:

Let’s go through some examples to understand when and how MalformedURLException can occur:

Example 1: Missing Protocol

try {
    URL url = new URL("www.example.com");
} catch (MalformedURLException e) {
    System.out.println("Malformed URL Exception: " + e.getMessage());
    e.printStackTrace();
}

Output:

Example 2: Illegal Characters

try {
    URL url = new URL("http://www.example.com/@invalid");
} catch (MalformedURLException e) {
    System.out.println("Malformed URL Exception: " + e.getMessage());
    e.printStackTrace();
}

Output:

Malformed URL Exception: Illegal character in path at index 23: http://www.example.com/@invalid
java.net.MalformedURLException: Illegal character in path at index 23: http://www.example.com/@invalid
    at java.net.URL.<init>(URL.java:614)
    at java.net.URL.<init>(URL.java:490)
    at java.net.URL.<init>(URL.java:439)
    ...

Conclusion

MalformedURLException is a common exception in Java that occurs when dealing with improperly formatted URLs. By understanding when it can occur and how to handle it, you can write more robust Java applications that deal with URL parsing and connections effectively.

GitHub – delta-dev-software/MalformedURLException-example

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