CODEWITHSUNDEEP
javaoop
Tom Tresansky
Tom Tresansky

Reputation: 19892

Why are protected members allowed in final java classes?

Why are protected members allowed in final classes?

Shouldn't this be a compile-time error?

Edit: as people have pointed out, you can get same package access by using the default modifier instead. It should behave in exactly the same manner, because protected is just default + sub-classes, and the final modifier explicitly denies subclassing, so I think the answer is more than just to provide same package access.

Upvotes: 20

Views: 6358

Answers (6)

vikas
vikas

Reputation: 1

package p;

import java.sql.Connection;

public final class ProtectedTest {
    String currentUser;
    Connection con = null;

    protected Object ProtectedMethod(){
        return new Object();
    }
    public ProtectedTest(){
    }
    public ProtectedTest(String currentUser){
        this.currentUser = currentUser;
    }
}

package p;

public class CallProtectedTest {
    public void CallProtectedTestMethod() {
        System.out.println("CallProtectedTestMethod called :::::::::::::::::");
        ProtectedTest p = new ProtectedTest();
        Object obj = p.ProtectedMethod();
        System.out.println("obj >>>>>>>>>>>>>>>>>>>>>>>"+obj);
    }
}

package p1;

import p.CallProtectedTest;

public class CallProtectedTestFromp2 {
    public void CallProtectedTestFromp2Method(){
        CallProtectedTest cpt = new CallProtectedTest();
        cpt.CallProtectedTestMethod();
    }

    public static void main(String[] args) {
        CallProtectedTestFromp2 cptf2 = new CallProtectedTestFromp2();
        cptf2.CallProtectedTestFromp2Method();
    }
}

Upvotes: -1

Tom Hawtin - tackline
Tom Hawtin - tackline

Reputation: 147154

The protected modifier is necessary on methods that override protected methods from a base class, without exposing those members to the public.

In general, you could introduce a lot of unnecessary rules to outlaw implausible combinations (such as protected static), but it wouldn't help much. You can't outlaw stupidity.

Upvotes: 18

Bozho
Bozho

Reputation: 597046

The argument stated here that protected members can be accessed by classes of the same package is valid, but in this case protected becomes equal to the default visibility (package-private), and the question remains - why are both allowed.

I'd guess two things:

  • no need to forbid it
  • a class may be made final temporarily, until a design decision is made. One should not go and change all visibility modifiers each time he adds or removes final

Upvotes: 7

irreputable
irreputable

Reputation: 45433

You can argue that, but there's no real harm anyway. A non-final class may also have a protected member, but no subclass, it won't bother anybody either.

Upvotes: 0

Affe
Affe

Reputation: 47954

The protected modifier also allows access within the same package, not just to subclasses. So it's not completely meaningless on a final class.

Upvotes: 10

skaffman
skaffman

Reputation: 403451

Because protected members can be accessed by other classes in the same package, as well as subclasses.

Upvotes: 15

Related Questions