Mastering Java: The Ultimate Quiz for 'Thinking in Java'

What does the invoke method within NullRobotProxyHandler do?

1. Calls the method of the proxied Robot instance

2. Logs the invocation for debugging

3. Throws an UnsupportedOperationException

4. Returns a hardcoded response for any method

The correct answer is: Calls the method of the proxied Robot instance

The invoke method within NullRobotProxyHandler serves as a way to interact with the null (uninitialized) robot object. Option A is the correct answer because it calls the method of the proxied Robot instance, meaning that it allows us to utilize the methods of the robot object even if it is currently null. Option B may seem like a possible answer, but this is incorrect because the role of the invoke method is not to provide logging information. Option C is incorrect because instead of throwing an exception, the method allows us to execute the proxied Robot instance's methods. Lastly, option D is incorrect because the invoke method does not provide a hardcoded response, but rather enables us to interact with the proxied Robot instance.