Java, A Beginner's Guide, 5th Edition, 5th Edition

Using Wildcard Arguments

As useful as type safety is, sometimes it can get in the way of perfectly acceptable constructs. For example, given the NumericFns class shown at the end of the preceding section, assume that you want to add a method called absEqual( ) that returns true if two NumericFns objects contain numbers whose absolute values are the same. Furthermore, you want this method to be able to work properly no matter what type of number each object holds. For example, if one object contains the Double value 1.25 and the other object contains the Float value –1.25, then absEqual( ) would return true. One way to implement absEqual( ) is to pass it a NumericFns argument, and then compare the absolute value of that argument against the absolute ...