使用Java中的重载方法键入顺序(Type order with overloaded methods in Java)

使用Java中的重载方法键入顺序(Type order with overloaded methods in Java)

给定Java中相同类的两种方法：

public void doSomething( Person person ); public void doSomething( Employee employee );

哪里

Employee extends Person

如果我打电话给：

doSomething( employee )

我发现doSomething（Person）被调用。

我曾预料过，与最接近的匹配合约被调用，而不是最抽象的（这正是我所发现的）

有人能解释为什么吗？

问候

马蒂

Given two methods on the same class in Java :

public void doSomething( Person person ); public void doSomething( Employee employee );

where

Employee extends Person

If I call:

doSomething( employee )

I find that doSomething( Person ) gets invoked.

I'd have expected the overload with the closest matching contract be invoked, not with the most abstract (which is what I'm finding)

Could someone explain why?

最满意答案

使用最具体的适用重载 - 但该重载是在编译时根据employee变量的编译时间类型确定的。

换一种说法：

Employee employee = new Employee(); doSomething(employee); // Calls doSomething(Employee)

但：

Person employee = new Employee(); doSomething(employee); // Calls doSomething(Person)

请注意，这与重写目标对象的执行时间类型非常重要。

The most specific applicable overload is used - but that overload is determined at compile-time, based on the compile time type of the employee variable.

In other words:

Employee employee = new Employee(); doSomething(employee); // Calls doSomething(Employee)

but:

Person employee = new Employee(); doSomething(employee); // Calls doSomething(Person)

Note that this is unlike overriding where it's the execution time type of the target object which is important.