[英]static <T extends Number & Comparable<? super Number>>
I have following class with one static method: 我有一个静态方法跟随类:
public class Helper {
public static <T extends Number & Comparable<? super Number>> Boolean inRange(T value, T minRange, T maxRange) {
// equivalent (value >= minRange && value <= maxRange)
if (value.compareTo(minRange) >= 0 && value.compareTo(maxRange) <= 0)
return true;
else
return false;
}
}
I try to call this method: 我试着调用这个方法:
Integer value = 2;
Integer min = 3;
Integer max = 8;
Helper.inRange(value, min, max) ;
Netbeans compiler show me this error message: Netbeans编译器显示此错误消息:
method inRange in class Helper cannot be applied to given types; 类Helper中的方法inRange不能应用于给定的类型; required: T,T,T found: java.lang.Integer,java.lang.Integer,java.lang.Integer reason: inferred type does not conform to declared bound(s) inferred: java.lang.Integer bound(s): java.lang.Number,java.lang.Comparable required:T,T,T found:java.lang.Integer,java.lang.Integer,java.lang.Integer reason:推断类型不符合推断的声明边界:java.lang.Integer bound(s) :java.lang.Number,java.lang.Comparable
Any ideas? 有任何想法吗?
thanks. 谢谢。
Try <T extends Number & Comparable<T>>
. 尝试<T extends Number & Comparable<T>>
。
Eg Integer
implements Comparable<Integer>
, which is not compatible with Comparable<? super Number>
例如, Integer
实现了Comparable<Integer>
,它与Comparable<? super Number>
不兼容Comparable<? super Number>
Comparable<? super Number>
(Integer is not a superclass of Number). Comparable<? super Number>
(整数不是Number的超类)。 Comparable<? extends Number>
Comparable<? extends Number>
would not work either because Java would then think the ?
Comparable<? extends Number>
也不会工作,因为Java会考虑?
could be any subclass of Number
, and passing a T
to compareTo
would then not compile because it expects a parameter of ?
可以是Number
任何子类,并且将T
传递给compareTo
则不会编译,因为它期望参数为?
, not T
. ,不是T
Edit: as newacct said, <T extends Number & Comparable<? super T>>
编辑:正如newacct所说, <T extends Number & Comparable<? super T>>
<T extends Number & Comparable<? super T>>
will work too (and be slightly more general) since then compareTo
will then accept any ?
<T extends Number & Comparable<? super T>>
也会起作用(稍微更一般),因为那时compareTo
会接受?
of which T
is a subclass, and as usual, an instance of a subclass can be given as a parameter where a superclass is expected. 其中T
是子类,并且像往常一样,子类的实例可以作为期望超类的参数给出。
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