Question

public class ProtectedClass {
    private String name;
    public static void changeName(ProtectedClass pc, String newName) {
        pc.name = newName;
    }
    public ProtectedClass(String s) { name = s; }
    public String toString() { return name; }
    public static void main(String[] args) {
        ProtectedClass 
            pc1 = new ProtectedClass("object1"),
            pc2 = new ProtectedClass("object2");
        pc2.changeName(pc1, "new string"); // expect ERROR/EXCEPTION
        System.out.println(pc1);
    }
} ///:~

Considering above Java source code,it could easily concluded that the Java programming language could only provide class-level access control/protect.Are there any programming languages providing object-level access control/protect?

thanks.

P.S:This problem is derived from this question Java: Why could base class method call a non-exist method?I want to give my appreciation to TofuBeer.

Answer 1

Scala has an object-private scope:

class A(){
    private[this] val id = 1
    def x(other : A) = other.id == id
}

<console>:6: error: value id is not a member of A
           def x(other : A) = other.id == id

It compiles if you change the visibility to private:

class A(){
    private val id = 1
    def x(other : A) = other.id == id
}