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JavaDiamondPatterns Interview Questions Toggle navigation In28Minutes Download Java Interview Pdf Guide Popular Video Courses Buy Java Interview Video Guide - $12.99/₹799 Start learning on Udemy today! JavaDiamondPatterns Interview Questions Idea overdue this vendible is to requite an overview ofDiamondPatterns and not really explain all the implementation details related to them. For me, understanding the nuts of a diamond pattern is important. The implementation details are secondary. Implementation details can hands be looked up when needed if I understand the context in which a diamond pattern applies. There are three variegated types ofDiamondPatterns Creational Patterns : Concerned with megacosm of Objects. Prototype, Singleton, Builder etc. Structural Patterns : Concerned with structure of Objects and the relationships between them. Decorator, Facade, Adapter etc. Behavioural Patterns : Concerned with interaction between objects. Strategy, Template Method etc. Creational Patterns Creational Patterns deal with megacosm of objects. Prototype Prototype is specified as “A fully initialized instance to be copied or cloned”. Let’s consider a Chess Game. At the start of the game, the way the pieces are serried on a workbench is the same. Following strategy can be used in a chess program to setup a new game: Create a fully initialized instance of a chess game with the correct positions for all pieces.This is the prototype. Whenever there is a need to create a new chess game, clone or reprinting the initial chess game prototype. Builder Builder pattern is usually used to hibernate the complexity of an object construction. Certain objects might have ramified internal structure. Every time an instance is created, the unshortened structure needs to be created. It is a good practice to hibernate this complexity from the dependant objects. And that’s where the Builder pattern comes in. Builder pattern is specified as “Separates object construction from its representation”. Example : Consider a fast-food restaurant offering a Vegetarian Meal and a Non Vegetarian Meal. A typical meal is a burger and a unprepossessed drink. Depending on the type of the meal, the burger is a vegetarian burger or a yellow burger. The drink is either an orange juice or a pineapple juice. The unelevated Builder matriculation can be used to create meal objects. public matriculation MealBuilder { public Meal buildVegMeal (){ Meal meal = new Meal(); meal.addItem(new VegetarianBurger()); meal.addItem(new OrangeJuice()); return meal; } public Meal buildNonVegMeal (){ Meal meal = new Meal(); meal.addItem(new ChickenBurger()); meal.addItem(new PineappleJuice()); return meal; } } Singleton Singleton is specified as “A matriculation of which only a single instance can exist (in a jvm). A good example of Singleton matriculation in Java is java.lang.System. If you are a Java guys, then these things might be useful: Best way to implement Singleton is using a Enum. Refer “Effective Java” by Joshua Bloch. JEE7 has inbuilt @Singleton voice-over with @Startup, @PostConstruct and @DependsOn("other beans") options Singletons make lawmaking difficult to unit test. In Spring, all beans are singletons by default (in the telescopic of using context). Structural Structural patterns deal with the structure of objects and their relationships. Proxy Proxy is specified as “An object representing flipside object”. A good example of a proxy is a Debit Card. It represents the wall worth but is really not the wall worth itself. It acts as a proxy to ourWallAccount. EJB’s typically have two interfaces - Remote and Home. Home interface is a good example of a proxy. Decorator Decorator is specified as “Add responsibilities to objects dynamically”. Let’s take an example of a Pizza shop offering 10 types of Pizzas. Currently these are specified using an inheritance chain. All these 10 pizza types proffer AbstractPizza class. Now, there is a new functionality requested - we would want to indulge 3 variegated types of toppings for each of the pizza type. We have two options Create 3 classes for each of the 10 pizza types resulting in a total of 30 classes. Use a topping decorator on top of AbstractPizza class. Usually the preference would be to use a decorator. Good example for decorator is the Java IOMatriculationStructure. To create a LineNumberInputStream we do something like LineNumberInputStream(BufferedInputStream(FileInputStream))). BufferedInputStream is a decorator for FileInputStream. LineNumberInputStream is a decorator for BufferedInputStream. Disadvantage of Decorator is the resulting complexity in creating objects. Facade Facade is specified as “A single matriculation that represents an unshortened subsystem”. A good example of facade in real life is an event manager. We tideway an event manager to organize an event and they would take superintendency of arranging everything related to the event - Decoration, Food, Invitations, Music Band etc. Let’s consider an using taking online orders for books. Following steps are involved. Check if there is stock and reserve the book. Make payment. Update stock Generate invoice Its preferred to create a facade tabbed OrderService which takes superintendency of all these steps. Facade moreover wilt a good place to implement transaction management. Advantages of a Facade: Reduced network calls Reduced coupling Helps in establishing transaction purlieus AdapterSpecifiedas “Match interfaces of variegated classes”. All the translators that we create to map one type of object to flipside type are good examples. A good real life example would be Power Adapters. BehaviouralUnitingof ResponsibilitySpecifiedas “A way of passing a request between a uniting of objects”. A good real time example is the Loan or LeaveClearanceProcess. When a loan clearance is needed, it first goes to the clerk. If he cannot handle it (large amount), it goes to his manager and so on until it is tried or rejected.Flipsidegood example is Exception Handling in most programming languages. When an exception is thrown from a method with no exception handling, it is thrown to the calling method. If there is no exception handling in that method too, it is remoter thrown up to its calling method and so on. This happens until an towardly exception handler is found. IteratorSpecifiedas “Sequentially wangle the elements of a collection”.Variegatedobjects might have variegated internal representations. Iterator defines one way of looping through the objects in a list or a hodgepodge or a map, so that the internal complexities are hidden. StrategySpecifiedas “Encapsulates an algorithm inside a class”. Typically used to decouple the algorithm or strategy used from the implementation of the matriculation so that the algorithm can be reverted self-sustaining of the class. A good example in Java is the Comparator interface. java.util.Comparator#compare() ObserverSpecifiedas “A way of notifying transpiration to a number of classes”. A good example is Online Bidding.Variegatedpeople can register as observers. They all are notified when there is a new bid. If you are a Java programmer, Observer diamond pattern is once built for you. Look up the Observer interface and Observable class. Template MethodSpecifiedas “Defer the word-for-word steps of an algorithm to a subclass”. Good example is a House Plan. A upper level floor plan is provided first. Within a floor plan, the foundation, framing, plumbing, and wiring will be identical for each house. Variations for each house can be widow in later - spare wing, wooden flooring/carpet, which verisimilitude to paint.Flipsideexample for Template Method is implementation of Spring AbstractController. The total spritz is implemented by handleRequest method. However, subclasses can tenancy the details by implementing the utopian method handleRequestInternal. (example simplified to focus only on necessary details) @Override public ModelAndView handleRequest(***) throws Exception { // Delegate to WebContentGenerator for checking and preparing. checkAndPrepare(request, response); HttpSession session = request.getSession(false); if (session != null) { Object mutex = WebUtils.getSessionMutex(session); return handleRequestInternal(request, response); } return handleRequestInternal(request, response); } protected utopian ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response) throws Exception; MementoSpecifiedas “Capture and restore an object's internal state”. In a number of games, we have the full-length to do an intermediate save and return to it at a later point. Implementing this needs using the Memeto pattern. We save the state of the game at the intermediate point so that we can return when to it.Flipsidegood example is the Undo / Redo Operations in text or image editing software. Software saves the intermediate state at various points so that we can hands return when to that state. MediatorSpecifiedas “Defines simplified liaison between classes”. A good example of Mediator is an Enterprise Service Bus. Instead of permitting applications to directly communicate with each other, they go through an ESB. A good real life example is Air Traffic Controller. All the flights talk to ATC to decide the route to take. Imagine the unconnectedness if each flight has to talk to all other flights to decide the route. If you loved these Questions, you will love our PDF Interview Guide with 400+ Questions. Download it now!. 400+ Interview Questions in 4 Categories: Java : Core Java, Advanced Java, Generics, Exception Handling, Serialization, Threads, Synchronization, Java New Features Frameworks : Spring, Spring MVC, Struts, HibernateDiamond: Design,DiamondPatterns,LawmakingReview Architecture : Architecture, Performance & Load Testing, Web Services, REST Web Services,Security, Continuous Integration Home Subscribe to: Posts (Atom) Best Selling Java Interview Udemy Course 400+ Java Interview Questions 25 Java Interview Videos Core Java Advanced Java Spring Spring MVC Struts Hibernate Generics Collections Java New FeaturesDiamondPatterns Web Services © Java Interview Questions and Answers For Freshers and Experienced 2013 . Powered by Bootstrap and Bootstrap Blogger Templates