Proper use of generics??

[Raymond Holguin]

I want to know if this is the proper way to accomplish my goal using generics. Basically I have 2 classes (ClassA & ClassB) and i want to create a function that will return either a List of ClassA or a list of ClassB....or possibly a mix of both depending on the parameter I pass. I figured in order to do this I would need to create this "Base" class that ClassA and ClassB would extend from that way I can use the generic wildcards. This works and it compiles, but I just want to know if this is the best way to accomplish my goal. Generics & wildcards really confuse the hell out of me so im trying to wrap my head around it with examples.

The reason i question it is because on my type casting in the main function i get type safety warnings and I would imagine i would not get those if i was doing this the "right" way
Type safety: Unchecked cast from List<capture#1-of ? extends Main.Base> to List<Main.ClassA>
Type safety: Unchecked cast from List<capture#1-of ? extends Main.Base> to List<Main.ClassB>

any input to my example would be greatly appreciated.
Thanks!!

public class Main {
	public static List<ClassA> list;
	public static List<ClassB> list2;
	public static List<? extends Base> list3;
	
	public static void main(String[] args) throws Exception {
		setListOfClassA((List<ClassA>)getClasses(0));
		setListOfClassB((List<ClassB>)getClasses(1));
		setListOfAllClasses(getClasses(2));
		
		System.out.print(Main.list);
		System.out.print(Main.list2);
		System.out.print(Main.list3);
	}
	
	public static void setListOfClassA(List<ClassA> list) {
		Main.list = list;
	}
	
	public static void setListOfClassB(List<ClassB> list) {
		Main.list2 = list;
	}
	
	public static void setListOfAllClasses(List<? extends Base> list) {
		Main.list3 = list;
	}
	
	public static List<? extends Base> getClasses(int type) {
		List<Base> list = new ArrayList<Base>();
		if(type == 0) {
			list.add(new ClassA());
		} else if (type == 1) {
			list.add(new ClassB());
		} else {
			list.add(new ClassA());
			list.add(new ClassB());
		}
		
		return list;
	}
	
	public static class Base {}
	public static class ClassA extends Base {}
	public static class ClassB extends Base {}
}