How are java.lang.Object's protected methods protected from subclasses?
- by Adrian Lang
The keyword protected grants access to classes in the same package and subclasses (http://java.sun.com/docs/books/tutorial/java/javaOO/accesscontrol.html).
Now, every class has java.lang.Object as superclass (http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Object.html).
Hence I conclude that every class may access java.lang.Object's methods even if they are protected.
Take a look at the following example:
public class Testclass {
public Object getOne() throws CloneNotSupportedException {
return this.clone();
}
public Object getTwo() throws CloneNotSupportedException {
return ((Object) this).clone();
}
}
While getOne() compiles fine, getTwo() gives
Testclass.java:6: clone() has protected access in java.lang.Object
return ((Object) this).clone();
I neither understand why getTwo() doesn't compile nor what's the difference (regarding the access of java.lang.Objects members) with getOne().
