In this method,

public static void printClass(Class<?> cl) {
  cl.getTypeParameters();
} 

the return type of cl.getTypeParameters() is TypeVariable<Class<capture of ?>>[], but why this result can assign to a variable with type TypeVariable<? extends Class<?>>[], that is

public static void printClass(Class<?> cl) {
  TypeVariable<? extends Class<?>>[] typeVariables = cl.getTypeParameters();
}

What I have known is that if

B[] b = new B[]{...};
A[] a = b;

then A must be some supertype of B. In other words, why TypeVariable<? extends Class<?>> is a supertype of TypeVariable<Class<capture of ?>>?