【正文】 t concept. Precisely because the abstract concepts in problem field no corresponding specific concept, so to characterization abstract concepts nonabstract class cannot be instantiated. In an objectoriented field, mainly used for class abstraction types hidden. We can construct a fixed a group of behavior of abstract description, but this group of behavior but can have any a possible concrete implementation. This abstract describe is abstract classes, and this an arbitrary a possible concrete realization is behaved for all possible derived class. Modules can be operating an abstract body. Due to the module dependent on a fixed abstraction body, so it can are not allowed to modify, Meanwhile, through the abstract derived from the body, also can expand the behavior of this module function. Familiar with OCP readers must know, objectoriented design to be able to achieve a core principle OCP (Open Closed flying), class abstraction is one of the key. From the perspectives of grammar definition abstract class and interface In grammatical perspective, Java language for abstract scaleup and with gives different definitions below to define a way, called produce professional Demo abstract class as an example to illustrate the difference. In the abstract scaleup manner, produce professional Demo can have their own data members, also can have the members of the abstract method, and with the realization of the way, produce professional Demo can have only static cannot be modified data members, all the members of the methods is abstract. In a sense, with a special kind of abstract class. From programming, from the perspective of abstract scaleup and with can be used to achieve cancel thoughts make themselves. But in the specific use top still have some difference. First, abstract class in Java language suggests is a kind of inheriting relationship, a class can be used only once inheritance relationship (because Java do not support more inheritance ZhuanZhu). However, a class but can implement multiple with. Maybe it is Java language designers in considering Java for multiple inheritance support of a promise to consider it. Secondly, in the definition of abstract scaleup, we may give methods of default behavior. But in with the definition of method cannot have the default behavior, to bypass this limits, must use entrust, but it will add some plexity, sometimes can cause a lot of trouble. In class abstraction cannot define the default behavior is there another serious problem that may cause on the maintenance of trouble. Because if later want to modify the interface (usually by such abstract scaleup or with to represent) to adapt to the new situation (., adding new methods or to have already used the method to add new parameters), will be very troublesome, might spend a lot of time (for a derived class many situation, especially). But if the interface is through scaleup abstract to realize, then may just need to modify defined in the abstract scaleup default behavior is ok. Similarly, if not in abstract class defined in the default behavior, can lead to the same method to appear in the abstract class every a derived class, violated aone rule, principle, causing aone place, the same code duplication against future maintenance. Therefore, in the abstract scaleup and with a choice between should be careful. From the design concept wi