java – 当方法之间的差异是参数子类型时,将null传递给重写方法

发布时间：2020-12-15 00:52:14 所属栏目：Java 来源：网络整理

导读：参见英文答案 Which overload will get selected for null in Java?3个 Strange Java null behavior in Method Overloading 4个 OUTPUT：乙为什么虚拟机调用此方法f(null){System.out.println(“B”);}？为什么不f(null){System.out.println(“A”);} publ

参见英文答案 > Which overload will get selected for null in Java?3个
> Strange Java null behavior in Method Overloading 4个
OUTPUT：乙

为什么虚拟机调用此方法f(null){System.out.println(“B”);}？

为什么不f(null){System.out.println(“A”);}

public class Test{

    public static class A {}
    public static class B extends A {}

    public void f(A a) {System.out.println("A");}
    public void f(B a) {System.out.println("B");}

    public static void main(String[] args) {
        new Test().f(null);
    }
}

解决方法

调用具有最特定参数类型的方法.这是规则
这是从 JLS section 15.12.2.5

If more than one member method is both accessible and applicable to a method invocation,it is necessary to choose one to provide the descriptor for the run-time method dispatch. The Java programming language uses the rule that the most specific method is chosen.

（编辑：李大同）

【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容!