小编arn*_*bef的帖子

当用Java做一些不太奇特的东西时,我遇到了泛型错误,我无法理解为什么它不起作用.代码是:

package test;
import java.util.*;
public class TestClass {
  public static class A extends C{}
  public static class B extends C{}
  public static class C{}
  public static class D<T>{}
  public static class E<T>{}

  public static void main(String args[]){
      E<D<? extends C>> a = new E<D<A>>();
      E<D<? extends Object>> b = new E<D<? extends C>>();
      E<D<? extends A>> c = new E<D<A>>();
      E<D<? super A>> d = new E<D<A>>();
      D<? extends C> e = new D<A>();
      D<? extends A> f = …