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Ans. It is a Design Pattern that facilitates loose coupling by sending the dependency information ( object references of dependent object ) while building the state of the object. Objects are designed in a manner where they receive instances of the objects from other pieces of code, instead of constructing them internally and hence provide better flexibility.
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Ans. MVC is a Design Pattern that facilititates loose coupling by segregating responsibilities in a Web application
1. Controller receives the requests and handles overall control of the request
2. Model holds majority of the Business logic, and
3. View comprise of the view objects and GUI component
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Ans. Factory Pattern deals with creation of objects delegated to a separate factory class whereas Abstract Factory patterns works around a super-factory which creates other factories.
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Ans. Builder is a creational Design Pattern whereas Composite is a structural design pattern. Composite creates Parent - Child relations between your objects while Builder is used to create group of objects of predefined types.
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Ans. Factory is a creational design pattern whereas Strategy is behavioral design pattern. Factory revolves around the creation of object at runtime whereas Strategy or Policy revolves around the decision at runtime.
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Ans. Subject has state, it keeps a list of observers. On the other hand, an Observable is really just a function that sets up observation. While Subjects are Observables, Subjects also implement an Observer interface.
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Ans. Adapter object has a different input than the real subject whereas Proxy object has the same input as the real subject. Proxy object is such that it should be placed as it is in place of the real subject.
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Ans. The Difference between these patterns in only the intent. Adapter is used because the objects in current form cannot communicate where as in Facade , though the objects can communicate , A Facade object is placed between the client and subject to simplify the interface.
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Singleton is used when we would like to reuse an object if object is not supposed to hold request or thread specific information. Inversely Prototype is used in situations where we would like to reuse the object information but the request / thread may require it own data to be persisted.
In short, Singleton is used in situations where we can live with single object being shared across multiple requests or threads whereas Prototype is used when we need duplicate copies of objects.
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Ans. Object Oriented Design Patterns is the science of identifying the pattern to make objects communicate in a way to effectively implement a Solution.
Factory Design Patterns is the pattern that recommends creation of separate Factory Object for creation of other object. So its like saying - If you want to create an object of ClassA, Talk to FactoryObject ( which is an object of FactoryClass ). FactoryObject in itself encapsulates the inputs and logic required to make the decision regarding the creation and construction of object.
Advantage of Factory Pattern - Loose Coupling and Segregation of Responsibilities. Now instead of hard binding the complete logic to decide the nature and shape of the object on the basis of some conditions, you are assigning the responsibility to some other object and hence making the relationship loosely coupled and hence main tenable.
Disadvantages - Before Understanding the Dis-advantages , we should understand that these patterns were chosen after a period of evolution and research and almost best fit for the required solution, otherwise these patterns would have easily been replaced by now.
Though the advantages of these pattern surpass the disadvantages keeping in mind the decreasing cost of resources and increasing scale of applications, but still loose coupling by means of additional objects results in decreased performance.
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Ans. Deserialization. In serialization, we can save the object of a byte stream into a file or send over a network. Suppose if you serialize the Singleton class, and then again de-serialize that object, it will create a new instance, hence deserialization will break the Singleton pattern.
To overcome this issue, we need to override readResolve() method in the Singleton class and return the same Singleton instance.
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Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)
BuggyBread buggybread = new BuggyBread("element1","element2");
BuggyBread.Builder builder = new BuggyBread.Builder();
BuggyBread.Builder builder = new BuggyBread.Builder("element1","element2");
Q25. Which of the following is not the difference between Singleton and Static class ( Class with static members only ) ?
a. Only one object can be created for Singleton class whereas No objects are created for static class. b. Singleton class instance is initiated using new keyword whereas static class instance is created using static method. c. Singleton class can be serialized whereas Static class cannot be. d. Singleton Class can participate in runtime Polymorphism whereas Static class cannot.
Ans. Singleton class instance is initiated using new keyword whereas static class instance is created using static method.
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Ans. It make sense only if we intend to modify either of the object and would like to preserve original state in other. Otherwise we can reuse the original object by making it singleton.
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Ans. The prototype pattern is a creational design pattern. It is used when the type of objects to create is determined by a prototypical instance, which is cloned to produce new objects. Prototype is used when we need duplicate copies of objects.
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Which of following class types in MVC holds Business logic ?
