Invoke static initializer

Question

Once a class is loaded is there a way to invoke static initializers again?

public class Foo {

    static {
     System.out.println("bar");
    }

}

Edit:

I need to invoke the static initializer because I didn't write the original class and the logic I need to invoke is implemented in the static initializer.

Answer 1

Put the initalisation code in a separate public static method, so you can call it from the static initializer and from elsewhere?

Answer 2

I agree with Earwicker's answer. Just extract the static initialization to a separate static method.

public class Foo {

    static {
        Foo.initialize();
    }

    public static void initialize() {
        System.out.println("bar");
    }

}

Answer 3

One circumstance in which the logic would be run more than once is if the class is loaded multiple times by different ClassLoaders. Note that in this instance, they are essentially different classes.

Generally, though, these are one-shot deals. If you want to be able to invoke the logic multiple times, do as others have suggested and put it in a static method.

Answer 4

you could try extending the class which contains the static code, and then put in your own static initializer. Not quite sure if it works, but :

public class OldBadLibraryClass {
   static {
      System.out.println("oldBadLibrary static init");
   }
}

//next file

public class MyBetterClass extends OldBadLibraryClass {
   static {
      System.out.println("MyBetterClass init");
   }
}


public class Test {
   public static void main(String[] args) {
      new MyBetterClass();
   }
}

see if the above prints in the order you expect. On my machine, it worked.

Though this is totally a hack, and is quite brittle. It would really be much better to modify the old class to have an init() method that can be overridden.