有关java泛型问题

[closed123]

Given:

classA {}

class B extends A {}

class C extends A {}

class D extends B {}

Which three statements are true? (Choose three.)

A. The type List<A> is assignable（分配） to List.

B. The type List<B> is assignable to List<A>.

C. The type List<Object> is assignable to List<?>.

D. The type List<D> is assignable to List<? extends B>.

E. The type List<? extends A> is assignable to List<A>.

F. The type List<Object> is assignable to any List reference.

G. The type List<? extends B> is assignable to List<? extends A>.

[coooliang]

泛型就是指定可以传进来的是啥
List<String> array = new ArrayList<String>();
这个容器只能接收字符串。其它的不行你不写 就可以接收所有的Object。
我觉得泛型主要是解决：出错在编译时出现而不是在运行时出现