【正文】 lize, 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 with abstract class and interface It mainly from grammar definition and programming perspective, this paper discusses the area with abstract class and don39。s understanding, whether for design intent reflect the correct and reasonable. We are a result analysis and description. If the two concepts are used with ways to define, then reflects two problems: 1, we may not understand clearly problem domain, AlarmDoor in concept essentially exactly is held or alarm? 2, if we in problem field understanding no problems, for example: we through for problem domain analysis found that AlarmDoor in concept in essence and filled is consistent, then we realize when he failed to correct reveal our design intention, because in these two concepts on the definitions (both use with defined) reflect reflected these meanings. If we in problem field understanding is: AlarmDoor in concept is essentially, at the same time it is filled with alarm function. How should we e to the design, realization to clear reflect what we mean by this? Front has said, in Java language abstract scaleup said in an inheritance relationship, and inheriting relationship is in nature is a relationship. So for held this concept, we should use abstract scaleup way to define. In addition, AlarmDoor has alarm functions, that it will be able to acplish alarm concept definition of behavior, so alarm concept can be through with defined. This realization basically can clearly reflect our for problem domain, the correct understanding of our design intent reveals. Actually the abstract scaleup says is is a relationship with said, was like a relationship, everyone when the choice can be used as a basis, which, of course, is based on understanding the problem domain, for instance: if we think AlarmDoor in concept is essentially alarm, have again at the same time, then held the function of the above definition way will in turn. Summary 1. Abstract scaleup in Java language suggests is a kind of inheriting relationship, a class can be used only once inheritance relationship. However, a class but can implement multiple with. 2 in the abstract scaleup may have their own data members, also can have the members of the abstract method, while in with, can have only static cannot be modified data members (. must is static, immigration, but in with generally doesn39。 abstract class 和 interface之間在對于抽象類定義的支持方面具有很大的相似性，甚至可以相互替換，因此很多開發(fā)者在進 行抽象類定義時對于 abstract class 和 interface 的選擇顯得比較隨意。并不是所有的類都是用來描繪對象的，如果一個類中沒有包含足夠的信息來描繪一個具體的對象，這樣的類就是抽象類。 在面向?qū)ο箢I(lǐng)域，抽象類主要用來進行類型隱藏。由于模塊依賴于一個固定的抽象體，因此它可以是不允許修改的；同時，通過從這個抽象體派生，也可擴展此模塊的行為功能。從某種意義上說， interface 是一種特殊形式的 abstract class。但是，一個類卻可以實現(xiàn)多個interface。 在抽象類中不能定義默認行為還存在另一個比較嚴重的問題，那就是可能會造成維護上的麻煩。因此，在 abstract class 和 interface 間進行選擇時要非常的小心。 前面已經(jīng)提到過， abstract class 在 Java 語言中體現(xiàn)了一種繼承關(guān)系，要想使得繼承關(guān)系合理，父類和派生類之間必須存在 isa關(guān)系，即父類和派生類在概念本質(zhì)上應該是相同的。 其他具體 的 Door 類型可以 extends 使用 abstract class 方式定義的 Door 或者implements 使用