私有方法可以在 java 中的 class 之外访问

Question

i have tried the following code in net beans i am expecting error but i didn't get any error

class B {

    private void method() {
    }

    public static void main() {
        B b = new B();
        B c = new C();
        b.method();
        c.method();
    }
}

class C extends B {
}

When c.method() tries to access the method it should show error but in NetBeans it is not showing. Please tell me what is the fault.

Answer 1

The way you have your method defined, you are calling C.method() from inside B.main() . Since method is private to B , the method is visible inside of B.main() even though the object is of type C which inherits from B .

Answer 2

The access checking is not done at object/class level, but rather at scope level. You call the method in B 's scope where it is accessible. It doesn't matter whether you call it on a C object or a B object.

Answer 3

That's because the main method is declared inside class B and has visibility to all B private methods.

When doing c.method() , the IDE knows that C extends B and it knows that main is inside B so it can see the private method (with referring to B ).

---

That's the "register" you'll find on the compiled B class (from Eclipse).

public static void main(java.lang.String[] args);
    new com.example.B [1]
    dup
    invokespecial com.neurologic.example.B() [17]
    astore_1 [b]
    invokespecial com.example.C() [20]
    astore_2 [c]
    aload_1 [b]
    invokespecial com.example.B.method() : void [21]
    aload_2 [c]
    invokespecial com.example.B.method() : void [21]
    return