java - 派生类可以减少对父类(super class)私有(private)方法的限制吗？

Question

基本上，你能做这样的事情吗？

class Base {
    private void foo(){
        println("Base");
    }
}
class Derived extends Base {
    public void foo(){
        println("Derived");
    }
}

Answer 1

在您的示例中，派生类的限制并没有减少。基类和派生类中的方法彼此无关。 方法Derived.foo()不会覆盖Base.foo()。因此，Base.foo(的私有(private)访问) 并未通过 Derived.foo() 减少限制。

Java 语言规范 Section 8.4.8, Inheritance, Overriding, and Hiding 对此进行了介绍。 。

8.4.8.1 Overriding (by Instance Methods)

An instance method mC declared in or inherited by class C, overrides from C another method mA declared in class A, iff all of the following are true:

• A is a superclass of C.
• C does not inherit mA.
• The signature of mC is a subsignature (§8.4.2) of the signature of mA.
• One of the following is true:
  • mA is public.
  • mA is protected.
  • mA is declared with package access in the same package as C, and either C declares mC or mA is a member of the direct superclass of C.
  • mA is declared with package access and mC overrides mA from some superclass of C.
  • mA is declared with package access and mC overrides a method m' from C (m' distinct from mC and mA), such that m' overrides mA from some superclass of C

简而言之，私有(private)方法不能被子类覆盖。如果您从基类调用私有(private)方法，它将调用该私有(private)方法，而不是子类中具有相同名称和签名的方法。