Why NoClassDefFoundError caused by static field initialization failure?

by

The answer to such questions is usually buried somewhere in the specs… (§12.4.2)

What happens when classes are initialized:

Steps 1-4 are somewhat unrelated to this question. Step 5 here is what triggers the exception:

5. If the Class object is in an erroneous state, then initialization is not possible. Release the lock on the Class object and throw a NoClassDefFoundError.

6-8 continue the initialization, 8 executes the initializers, and what usually happens is in step 9:

9. If the execution of the initializers completes normally, then lock this Class object, label it fully initialized, notify all waiting threads, release the lock, and complete this procedure normally.

But we got an error in the initializer so:

10. Otherwise, the initializers must have completed abruptly by throwing some exception E. If the class of E is not Error or one of its subclasses, then create a new instance of the class ExceptionInInitializerError, with E as the argument, and use this object in place of E in the following step. But if a new instance of ExceptionInInitializerError cannot be created because an OutOfMemoryError occurs, then instead use an OutOfMemoryError object in place of E in the following step.

Yep, we see an ExceptionInInitializerError b/c of the null pointer exception.

11. Lock the Class object, label it erroneous, notify all waiting threads, release the lock, and complete this procedure abruptly with reason E or its replacement as determined in the previous step. (Due to a flaw in some early implementations, a exception during class initialization was ignored, rather than causing an ExceptionInInitializerError as described here.)

And then the class is marked erroneous which is why we get the exception from step 5 the second time.

The surprising part is the third printout which shows that TestClass.class in MainClass actually holds a reference to a physical Class object.

Probably because TestClass still exists, it’s just marked erroneous. It has been already loaded and verified.

More Related Contents:

  1. Static Initialization Blocks
  2. When does static class initialization happen?
  3. When are static variables initialized?
  4. When does static initialization happen?
  5. Java : in what order are static final fields initialized?
  6. class fields Initialization sequence in Java
  7. Static class instance inside class
  8. What does the ‘static’ keyword do in a class?
  9. What is the reason behind “non-static method cannot be referenced from a static context”? [duplicate]
  10. Difference between Static methods and Instance methods
  11. Getting the class name from a static method in Java
  12. Why can’t we have static method in a (non-static) inner class (pre-Java 16)?
  13. Why can’t we use ‘this’ keyword in a static method
  14. Default values and initialization in Java
  15. Why can’t I declare static methods in an interface?
  16. Invoking a static method using reflection
  17. static allocation in java – heap, stack and permanent generation
  18. Receiving “wrong name” NoClassDefFoundError when executing a Java program from the command-line
  19. How do I mock static methods in a class with easymock?
  20. Are static variables inherited
  21. When to use static variables/methods and when to use instance variables/methods in Java? [closed]
  22. JavaFX Exception in thread “main” java.lang.NoClassDefFoundError: javafx/application/Application
  23. @Autowired and static method
  24. java.lang.NoClassDefFoundError: com/google/common/collect/ImmutableMap error using GeckoDriver Firefox through Selenium in Java
  25. Java: how to initialize String[]?
  26. Should all methods be static if their class has no member variables
  27. Why is a static class illegal in Java?
  28. Is an enum constant-specific class body static or non-static?
  29. Static variables and multithreading in java
  30. java.lang.NoClassDefFoundError when using MongoDB driver

Leave a Comment