The document discusses the importance of validating method parameters in Java to ensure reliability and avoid unexpected exceptions or incorrect results. It outlines when to check parameters, such as in public, protected, and package methods, and notes that checks may be omitted in certain scenarios, like private methods or when an implicit check is performed. The emphasis is on the 'fail fast' principle to enhance code robustness.

1. Writing Effective Methods in Java
Parag Shah
http://www.diycomputerscience.com

2. Always check method parameters for validity

3. WHY ?
Because we should always fail fast !

4. An example

5. What will happen if we do not ?
We may get an Exception which is unrelated
We may get an incorrect result
We may create an object which will fail at a totally
different and unrelated time

6. What should be checked ?
Constructors
Public, protected, package methods

7. When not to check ?
If the check is very expensive
a method which expects a sorted list
If the check will be done implicitly in the
computation
sorting automatically checks for comparable
instances
Possible to omit checks in private methods