code: @Override
      public void visitClassContext(ClassContext classContext) {
          try {
              ifBlocks = new ArrayList<>();
              loadedRegs = new HashMap<>();
              loopLocations = new BitSet();
              stack = new OpcodeStack();
              super.visitClassContext(classContext);
          } finally {
              ifBlocks = null;
              loadedRegs = null;
              loopLocations = null;
              stack = null;
          }
      }
docs: overrides the visitor to initialize and tear down the opcode stack
  
  @param classContext
  the context object of the currently parsed class