Class merging - breaking Concurrency?

Question

Hello there,
I use a class-merging tool for my applet development because applet-size does really a lot for what I am creating.
The class-merger does "nothing" more than to copy two classes into one and to add an int-field clalled "classTypeField". If two methods are named equal and may not renamed (e.g. because both classes implement Runnable) it does:
public void run() {
  if(classTypeField == -1)
  run_class1();
}else
if(classTyoeField == 0)
   run_class2();
}The class-type field is initialized in a modified constructor and which looks like this (copied from decompiled code):
public int classTypeField;
    public DecrypterInputStream(InputStream is,
                    EncrypterOutputStream decrypter, int i) {
     decrypter$1e835275 = decrypter;
     this.is = is;
        this.classTypeField = -1;
    }Am I right when assuming that this code is broken?
I am not completly sure, but if e.g. the run() method is executed on another thread than the thread the object was created it could be that the if(classTypeField==-1)-check would see a wrong value, right?
For Java-5+ its enough to add a "final"-keyword, for java<5.0 the classTypeField has to volatile, right?
Or am I missing some guarantees made by the JVM?
Thank you in advance, lg Clemens

Answer 1

Thanks a lot for your detailed answer.
The issue is then how the object is published such that other threads can use it. I have some problems to identify use-cases which could be problematic. Are there typical use-cases where such problems could be visible? My classes are mostly "manager-classes" instatiated on the EDT and used by some threads.
Should I recommend the tool-writers to make the classTypeField final? I guess they'll hate it because it means they would have to initialize it in any case and for now they relied on beeing 0 if not set ;)
Thanks a lot for your helpful and detailed answers all the time, lg Clemens