Can somebody explains why the last line of code doesn't compile ?

public class TestClassArray {
    private static class A {
    }
    private static class B extends A {
    }
   
    Class[] rawClasses = { B.class }; // warning
   
    Class<?>[] wildcardsClasses = { B.class };
   
    // error : Cannot create a generic array of Class<? extends
TestClassArray.A>
    Class<? extends A>[] upperBoundClasses = { B.class };
}