【正文】 es, use abstract classes for us any good? In objectoriented concept, we know all objects is through class to describe, but in turn not such. Not all classes are used to describe object, if a class does not contain enough information to portray a concrete object, this class is abstract classes. Abstract classes are often used to characterization of problem field in our analysis, design that the abstract concepts, is to the series will look different, but essentially the same exact conception of abstraction. For example: if we carry out a graphical editing software development, will find problem domain exists round, triangle so some specific concept, they are different, but they all belong to shape such a concept, shape this concept in problem domain is not exist, it is an abstract 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 int