Thread: Static fields and inheritance

Setup: Java SE 6. Previous/future versions of Java may be different, I haven't tried them out yet.

If you declare a static variable, by default it doesn't get inherited:

public class Base
{
     public static int x = 5;
}

public class Derived extends Base
{
     static
     {
          x = 3; // this is changing Base's x
     }
}

public class Main
{
     public static void main(String[] args)
     {
          System.out.println(Derived.x); // Will spit out an error, need to access the method statically, or from Base
          System.out.println(Base.x); //  prints out "3" because the static Derived got built second
     }
}

However, if you have your Derived class declare a static variable x:

public class Derived extends Base
{
     public static int x; // may get a warning about variable hiding
     static
     {
          x = 3; // Derived's x is change, Base x is still 5
     }
}

Then you can use the two instance variables separate denoted by the class name. Note that from this method, it's not even necessary to force the two variables to the same type.

public class Derivved extends Base
{
     public static String x = "Hello"; // again, there may be a warning about variable hiding
}