在Java中使用泛型时遇到编译问题
public class Subject<T>{
private long id;
private T data;
//..
public T getData() {
return this.data;
}
}
import com.res.emorobots.observer.OrdersIterableObserver;
public class OrdersIterableSubject<T1 extends Collection<OrdersIterableObserver<T2>> ,T2 extends Collection<Order>> extends Subject<Collection<OrdersIterableObserver<T2>>>{
private long id;
private T2 data;
protected T1 observers;
public T2 getData() {
return this.data;
}
}
错误: 这行有多个标记 -返回类型与Subject >>。getData()不兼容 -覆盖 com.res.emorobots.subject.Subject >>。getData
有什么想法吗?谢谢您。
答案 0 :(得分:0)
select l.id, cl.Category_ID
from
listings as l inner join CategoryListings as cl
on l.id=cl.Listing_ID
inner join Categories as c on c.ID = cl.Category_ID
where c.id in (select id from Categories where id =1 or id=3)
扩展了OrdersIterableSubject
,因此其Subject<Collection<OrdersIterableObserver<T2>>>
方法必须返回:
getData
(或子类型)