code: @Override
      public void visitClassContext(ClassContext classContext) {
          try {
              stack = new OpcodeStack();
              possibleForLoops = new HashSet<>();
              super.visitClassContext(classContext);
          } finally {
              stack = null;
              possibleForLoops = null;
          }
      }
docs: overrides the interface to create and clear the stack and loops tracker
  
  @param classContext
  the context object for the currently parsed class