最病 A Incompatible changes 口 Deleting fields n Moving classes up or down the hierarchy a Changing a nonstatic field to static or a nontransient field to transient a Changing the declared type of a primitive field n Changing the write object or readobject method so that it no longer writes or reads the default field data or changing it so that it attempts to write it or read it when the previous version did not. Institute of Computer Software 2021/1/28 Nanjing UniversityIncompatible changes  Deleting fields  Moving classes up or down the hierarchy  Changing a nonstatic field to static or a nontransient field to transient  Changing the declared type of a primitive field  Changing the writeObject or readObject method so that it no longer writes or reads the default field data or changing it so that it attempts to write it or read it when the previous version did not. 2021/1/28 Institute of Computer Software Nanjing University 35