code: @Override
      public void visitClassContext(ClassContext classContext) {
          try {
              JavaClass cls = classContext.getJavaClass();
              int major = cls.getMajor();
              if (major >= Const.MAJOR_1_5) {
                  stack = new OpcodeStack();
                  super.visitClassContext(classContext);
              }
          } finally {
              stack = null;
          }
      }
docs: implements the visitor to check for class file version 1.5 or better
  
  @param classContext
  the context object of the currently parsed class