code: @Override
      public void visitClassContext(ClassContext classContext) {
          try {
              if ((runtimeExceptionClass != null) && (exceptionClass != null)) {
                  stack = new OpcodeStack();
                  declaredCheckedExceptions = new HashSet<>(6);
                  JavaClass cls = classContext.getJavaClass();
                  classIsFinal = cls.isFinal();
                  classIsAnonymous = cls.isAnonymous();
                  super.visitClassContext(classContext);
              }
          } finally {
              declaredCheckedExceptions = null;
              stack = null;
          }
      }
docs: overrides the visitor to create the opcode stack
  
  @param classContext
  the context object of the currently parsed class