Throw exceptions inside a method versus declaring that a method can throw exceptions

[pwgit-create]

Let's discuss the difference between throwing a NullPointerException inside a method versus
declaring that a method can throw a NullPointerException.

1. Throwing a NullPointerException Inside a Method:

When you explicitly throw a NullPointerException inside a method, it means that your code is intentionally
causing this exception to be thrown under certain conditions. This usually happens when you want to signal an
error condition in your application logic.

Example:

public void someMethod(Object obj) {
    if (obj == null) {
        throw new NullPointerException("Object must not be null");
    }
    // Rest of the method's code...
}

In this example, a NullPointerException is explicitly thrown if the input parameter obj is null. This
provides clear error signaling and can include an informative message.

2. Declaring that a Method Throws a NullPointerException:

Declaring that a method throws a NullPointerException in its signature (using the throws keyword) means you're
specifying that this exception could be thrown as part of the normal execution flow of the method, and callers
need to handle it.

Example:

public void someMethod(Object obj) throws NullPointerException {
    // Method implementation...
}

Here, you're indicating that the someMethod might throw a NullPointerException. This doesn't mean you will
always throw this exception; it's more about documenting potential exceptions that can occur during method
execution.

Key Differences:

1. Intentional vs. Potential Exception:

   • Throwing a NullPointerException inside a method is intentional and specific to certain conditions.
   • Declaring a method throws a NullPointerException indicates that the exception could potentially be thrown,
     but it doesn't necessarily mean you're actively throwing it within the method.

2. Error Handling:

   • When you explicitly throw an exception, it's often done in response to invalid inputs or unexpected
     conditions.
   • Declaring exceptions in a method signature provides information to callers about what they need to handle.

3. Usage Context:

   • Throwing an exception is used for error signaling and typically accompanied by specific conditions (like null
     checks).
   • Declaring exceptions in a method signature is more about API documentation, informing users of the possible
     exceptions that might be thrown so they can handle them appropriately.

Practical Considerations:

• If you expect certain conditions to lead to NullPointerException, it's usually better to explicitly throw the
  exception with an informative message.
• Declaring exceptions in a method signature is generally used for more general or anticipated error scenarios,
  such as network issues (IOException) or resource constraints (SQLException).

In summary:

• Throwing an exception inside a method signals an intentional action based on specific conditions.
• Declaring that a method throws an exception indicates potential errors callers should be aware of and
  prepared to handle.

[lilstiffy]

Really good read and I've learned something new, thanks! 👌