In reading page 9 and 10 of this book - Ivor recommends that when you run your JDK 5.0 java programs, it is recommended that you use the -enableassertions or -ea option because you will always be using assertions.
What is assertions? What is the program asserting?
I looked it up in an online dictionary and the definition is:
Something declared or stated positively, often with no support or attempt at proof.