NullPointer Exception when using reflection

[jyu]

I'm not sure if I am writing bad code or this is a bug, but I cannot seem to get GL11.glGenLists() to work when using reflection. 

First, here is the exception when I run the app:

Exception in thread "main" java.lang.NullPointerException
        at org.lwjgl.opengl.GL11.glGenLists(GL11.java:1326)
        at Strip.<init>(Strip.java:31)
        at Strip.<init>(Strip.java:17)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:494)
        at java.lang.Class.newInstance0(Class.java:350)
        at java.lang.Class.newInstance(Class.java:303)
        at ModelTest.<init>(ModelTest.java:72)
        at ModelTest.main(ModelTest.java:64)

Here is Strip.java:31 :

ListDescriptor =  GL11.glGenLists(1);

As you can probably deduce from the stack trace, call to glGenLists is made inside the constructor.  I instantiate the class using reflection.

Here is ModelTest.java:71-73:

cls = Class.forName(className);
object = cls.newInstance();
method = cls.getMethod("draw",null)

When I replaced the above reflection code with a regular constructor call, everthing works fine. 

[ndhb]

Display is created already? I assume. Maybe reflection creates a new thread? I don't know much the API though.

[jyu]

It's interesting that you should bring up threading.  I am not familiar with API myself, but what effect does multithreading have on GenLists?

[Fool Running]

It's interesting that you should bring up threading.  I am not familiar with API myself, but what effect does multithreading have on GenLists?

OpenGL can not be accessed from multiple threads (Well, technically it can, but its not pretty ). If you try to access OpenGL from a different thread than the one OpenGL was created on, you will get that exception (The null ref). So I would guess that reflection is using a different thread.