Question

I’m looking at the documentation of JasperReports and I do not understand the return type of the following method:

public java.lang.Class<?> getValueClass()

Answer 1

Class<?> refers to any instance of Class. As compared to Class<? extends Collection> which would narrow the criteria down to a limited group of classes (those that extend Collection).

This is particularly important when calling methods like newInstance. If you have Class<?> a and call a.newInstance() you’ll get an Object. if you have Class<? extends Collection> and call b.newInstance() you’ll get an instance of Collection.