java - 为什么重载与 Java 中的继承一起工作？

Question

我们知道重载不适用于 C++ 中的派生类。但是为什么这种行为在java中是不同的呢？意味着为什么重载适用于 java 中的派生类？考虑以下来自 Stroustrup 博士常见问题解答的示例

#include <iostream>
using namespace std;
class Base
{
public:
    int f(int i)
    {
        cout << "f(int): ";
        return i+3;
    }
};
class Derived : public Base
{
public:
    double f(double d)
    {
        cout << "f(double): ";
        return d+3.3;
    }
};
int main()
{
    Derived* dp = new Derived;
    cout << dp->f(3) << '\n';
    cout << dp->f(3.3) << '\n';
    delete dp;
    return 0;
}

这个程序的输出是:

f(double): 6.3

f(double): 6.6

而不是假定的输出:

f(int): 6

f(double): 6.6

但是如果我们在 java 中执行此程序，则输出会有所不同。

class Base
{
    public int f(int i)
    {
        System.out.print("f (int): ");
        return i+3;
    }
}
class Derived extends Base
{
    public double f(double i)
    {
        System.out.print("f (double) : ");
        return i + 3.3;
    }
}
class Test
{
    public static void main(String args[])
    {
        Derived obj = new Derived();
        System.out.println(obj.f(3));
        System.out.println(obj.f(3.3));
    }
}

Answer 1

之所以有效，是因为 Java 语言规范在 §8.4.9. Overloading 中明确允许这样做:

If two methods of a class (whether both declared in the same class, or both inherited by a class, or one declared and one inherited) have the same name but signatures that are not override-equivalent, then the method name is said to be overloaded.

另见 §15.12.2. Compile-Time Step 2: Determine Method Signature .