关键词: 行为子类型, 契约, 前置条件, 后置条件, 不变式

Abstract:

A notion of behavior subtyping and its extension was introduced.By analysing an example of Java,how to design in object-oriented programming by contract was discussed in order to keep the features of single and multiple inheritance.The effectivity of the method was demonstrated.Finally,how to assign blame when contracts were violated in dynamic enviroment was discussed. The perspective of contract used in software development was outlooked.

Key words: behavior subtyping, contract, precondition, postcondition, invariant