可能是调用的子程序方法 改了, 主程序 没有重新编译 。
https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.3.2
Character Type Interpretation ------------------------------------------ B byte signed byte C char Unicode character D double double-precision floating-point value F float single-precision floating-point value I int integer J long long integer L<classname>; reference an instance of class S short signed short Z boolean true or false [ reference one array dimension