Java泛型:类型参数T隐藏类型T [英] Java generics: the type parameter T is hiding the type T
本文介绍了Java泛型:类型参数T隐藏类型T的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
为什么java编译器在translate方法中给我类型参数T隐藏了类型T?
public static interface Translator< T,E> {
电话(T t);
}
public static< T,E>列表与LT E - 代替; translate(List< T> 1,Translator< T,E> t){
..
}
如果我删除类型参数T
public static< E>列表与LT E - 代替; translate(List 1,Translator< T,E> t)
警告消失,但现在我不能做
$ b $
列表< Long> l = new ArrayList<>();
列表< String> r = translate(l,new Translator< Long,String>(){..})
它给了我这个错误
$ pre $ lt; code>方法translate(List< T>,GFn.Translator< T,E>)$ b $ (List< Long>,new GFn.Translator< Long,String>(){})
$ p是不适用于参数
$ p>
解决方案
我使用下面的代码,并且不会收到任何警告消息:
public class Main {
public static interface Translator< T,E> {
电话(T t);
}
public static< T,E>列表与LT E - 代替; translate(List< T> 1,Translator< T,E> t){
List< E> result = new ArrayList< E>(); (T item:l)
(
result.add(t.call(item));
}
返回结果;
}
public static class TranslatorImpl implements Translator< Long,String> {
@Override
public String call(Long aLong){
return String.valueOf(aLong);
$ b public static void main(String [] args)throws IOException {
List< Long> items = new ArrayList< Long>();
items.add(10L);
items.add(20L);
items.add(30L);
System.out.println(translate(items,new TranslatorImpl()));
}
}
Why java compiler is giving me "the type parameter T is hiding the type T" in the "translate" method ?
public static interface Translator<T, E> {
E call(T t);
}
public static <T, E> List<E> translate(List<T> l, Translator<T, E> t) {
..
}
If i remove the type parameter T
public static <E> List<E> translate(List<T> l, Translator<T, E> t)
the warning disappeared but now i cannot do
List<Long> l = new ArrayList<>();
List<String> r = translate(l, new Translator<Long, String>() { .. })
cause it give me this error
The method translate(List<T>, GFn.Translator<T,E>)
in the type GList is not applicable for the arguments
(List<Long>, new GFn.Translator<Long,String>(){})
解决方案
I'm using the following code and don't get any warning messages:
public class Main {
public static interface Translator<T, E> {
E call(T t);
}
public static <T, E> List<E> translate(List<T> l, Translator<T, E> t) {
List<E> result = new ArrayList<E>();
for (T item: l) {
result.add(t.call(item));
}
return result;
}
public static class TranslatorImpl implements Translator<Long, String> {
@Override
public String call(Long aLong) {
return String.valueOf(aLong);
}
}
public static void main(String[] args) throws IOException {
List<Long> items = new ArrayList<Long>();
items.add(10L);
items.add(20L);
items.add(30L);
System.out.println(translate(items, new TranslatorImpl()));
}
}
这篇关于Java泛型:类型参数T隐藏类型T的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
查看全文