问题描述
我有一个父类A，它的子类B.两个都具有doSomething方法，且参数类型为diff.
I have a parent class A, and its child B. Both are having doSomething method with diff type of parameters.
A级
package Inheritance;
public class A {
public void doSomething(Object str){
System.out.println("Base impl:"+str);
}
}
B级
package Inheritance;
public class B extends A{
public void doSomething(String str){
System.out.println("Child impl:"+str);
}
public static void main(String[] args) {
A a = new B();
a.doSomething("override");
}
}
运行此命令时，我得到"Base impl:override"作为输出！
When I run this, I'm getting "Base impl:override" as the output!
a指向B的对象，而他传递的参数是String，那么它不应该调用B的doSomething(String str)方法吗?
a is pointing to an object of B, and the he passed argument is String, So shouldn't it call B's doSomething(String str) method?
推荐答案
使用类型A的引用时，您只会看到为类A定义的方法.由于B中的doSomething不会覆盖doSomething在A中(因为它具有不同的签名)，因此不会调用它.
When you are using a reference of type A, you see only the methods defined for class A. Since doSomething in B doesn't override doSomething in A (since it has a different signature), it is not called.
如果要使用类型B的引用，则这两种方法均可用，并且会选择B的doSomething，因为它具有更具体的参数(字符串与对象).
If you were to use a reference of type B, both methods would be available, and doSomething of B would be chosen, since it has a more specific argument (String vs Object).
这篇关于在这种情况下，为什么要调用父类方法而不是子类?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！