Java方法调用重载逻辑 [英] Java method call overloading logic

问题描述

对于以下代码，为什么要打印A，B？我希望它打印B，B。
此外，JVM执行的方法调用是动态还是静态评估？

For the following code why does it print A, B? I would expect it to print B, B. Also, does the method call performed by the JVM is evaluated dynamically or statically?

public class Main {
    class A {

    }

    class B extends A {

    }

    public void call(A a) {
        System.out.println("I'm A");
    }

    public void call(B a) {
        System.out.println("I'm B");
    }


    public static void main(String[] args) {

        Main m = new Main();
        m.runTest();
    }

    void runTest() {
        A a = new B();
        B b = new B();

        call(a);
        call(b);
    }

}

推荐答案

编译器确定静态重载。 覆盖在执行时完成，但这不是一个因素。

Overloading is determined statically by the compiler. Overriding is done at execution time, but that isn't a factor here.

静态类型 a 是A，因此第一个方法调用被解析为 call（A a）。

The static type of a is A, so the first method call is resolved to call(A a).

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