1 class A {}
2 class B extends A {}
3 class C extends A {}
4 class D extends B {}
5 Which four statements are true ?
1 The type List<A>is assignable to List.对
2 The type List<B>is assignable to List<A>.错
3 The type List<Object>is assignable to List<?>.对
4 The type List<D>is assignable to List<?extends B>.对
5 The type List<?extends A>is assignable to List<A>.错
6 The type List<Object>is assignable to any List reference.错
7 The type List<?extends B>is assignable to List<?extends A>.对
原文：http://www.cnblogs.com/lyr612556/p/7846169.html