Question

this seems to be a newbie question, In Java, how can I check at compile time if someClass.class is derived from a anotherClass.class or at run-time if at compile time is not possible?

Answer 1

In code:

anotherClass.class.isAssignableFrom( someClass.class );

If you want to also check that the other class is a real class (and not an interface) add in a call to isInterface():

!anotherClass.class.isInterface() && anotherClass.class.isAssignableFrom( someClass.class );

Example:

System.out.println( Number.class.isAssignableFrom( Integer.class )); // true

Note that instanceof won’t work for you because you don’t have instances, only classes.

Excerpt from Javadoc for Class.isAssignableFrom:

Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter. It returns true if so; otherwise it returns false. If this Class object represents a primitive type, this method returns true if the specified Class parameter is exactly this Class object; otherwise it returns false.