我可以对 Number 基类进行算术运算吗? [英] Can I do arithmetic operations on the Number baseclass?

问题描述

我正在尝试用 Java 创建一个通用类，它将对数字执行操作.在下面的例子中，加法如下:

I am trying to create a generic class in Java that will perform operations on numbers. In the following example, addition, as follows:

public class Example <T extends Number> {

    public T add(T a, T b){
        return a + b;
    }

}

请原谅我的天真，因为我对 Java 泛型比较陌生.此代码无法编译并显示错误:

Forgive my naivety as I am relatively new to Java Generics. This code fails to compile with the error:

未定义参数类型 T、T 的运算符 +

The operator + is undefined for the argument type(s) T, T

我认为通过添加扩展数字"代码可以编译.是否可以执行此 Java，或者我是否必须为每个 Number 类型创建覆盖方法?

I thought that with the addition of "extends Number" the code would compile. Is it possible to do this Java or will I have to create overridden methods for each Number type?

推荐答案

Number 没有 + 操作符与之关联，也没有操作符重载.

Number does not have a + operator associated with it, nor can it since there is no operator overloading.

不过这样就好了.

基本上，您要求 java 自动装箱 Number 的后代，它恰好包括 Integer、Float 和 Double，可以自动装箱并应用加号运算符，但是，可能有任意数量的 Number 的其他未知后代不能被自动装箱，直到运行时才能知道.(该死的擦除)

Basically, you are asking java to autobox a descedant of Number which happens to include Integer, Float and Double, that could be autoboxed and have a plus operator applied, however, there could be any number of other unknown descendants of Number that cannot be autoboxed, and this cannot be known until runtime. (Damn erasure)

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