What is the difference between protected and default (package-private) access in Java?

Default access is like a society's internal notice: only residents of the same building (package) can see it. Protected is that plus family: a relative (subclass) living in another city (package) may also use it, as a relative.

The order from widest to narrowest is public, protected, default (no keyword), private.

package bank;
public class Account {
    protected double balance;      // package + subclasses
    double branchCode;             // package only
}

package bank.partner;
import bank.Account;
public class PartnerAccount extends Account {
    void show() {
        System.out.println(balance);     // ok: inherited
        // System.out.println(branchCode); // error: not visible
    }
}

A subclass in another package reaches protected members only on its own type, not on an arbitrary Account object.

• Thinking default access is the same as public or that it reaches subclasses in other packages.