Although usually easier to debug than other, more insidious erroneous behaviors, class-casting error messages are often symptoms of conceptual errors in recursively descending a composite data structure.

• 类型转换错误信息通常表明在递归下行一个复合数据结构时出现概念性错误,虽然它通常比其它错误更易调试,但也具有更多隐蔽的错误行为。