code: @Override
      public void visitClassContext(ClassContext classContext) {
          try {
              branchTargets = new BitSet();
              catchTargets = new BitSet();
              stack = new OpcodeStack();
              super.visitClassContext(classContext);
          } finally {
              branchTargets = null;
              catchTargets = null;
              stack = null;
          }
      }
docs: implements the visitor to create and clear the branchTargets
  
  @param classContext
  the context object for the currently parsed class