62,614
社区成员
发帖
与我相关
我的任务
分享
Collection<Pair<String, Long>> c1 = new ArrayList<Pair<String, Long>>();
Collection<Pair<String, Long>> c2 = c1; // s1
Collection<Pair<String, ?>> c3 = c1; // s2
Collection<? extends Pair<String, ?>> c4 = c1; // s3
Collection<SubTypeOfPair<String, Long>> c1 = new ArrayList<SubTypeOfPair<String, Long>>();
Collection<Pair<String, Long>> c2 = c1; // s4
Collection<SubTypeOfPair<String, Long>> c3 = c1; // s5
Collection<Pair<String, ?>> c4 = c1; // s6
Collection<? extends Pair<String, ?>> c5 = c1; // s7
List<User> userlist=new ArrayList<User>();
....
User u=userlist.get(0);
List<?> userlist=new ArrayList<?>();
....
User u=(User)userlist.get(0);