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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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Ans. Exception Handling Throw mechanism. | ||||
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Ans. Listeners. | ||||
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Ans. Setter injection Constructor injection Interface injection Look-up method/method injection | ||||
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Ans. matcher.find() should have been used instead of matcher.next() within while. | ||||
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Ans. Both are creational design patterns. 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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Very Frequently asked to Senior Software Engineers or Developers. | ||||
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Ans. [Open Ended Answer] | ||||
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Ans. Authentication / Authorization URL forwarding Auditing / Logging Localization | ||||
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Ans. Observable is emiting data and Observer is subscribing to catch the data | ||||
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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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Ans. I would choose Eager as the cost for 1 additional object is too minute for any such consideration. Eager Loading results in Faster access ( Object available at load time) at the cost of additional space. Lazy loading results in space saving ( Object available at first use ) at the cost of access speed. | ||||
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Ans. Strategy deals only with decision making at runtime so Interfaces should be used. | ||||
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Ans. split() and macthes() | ||||
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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) | ||||
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Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html | ||||
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Ans. String str = new StringBuilder().append("Buggy").append("Bread").toString(); | ||||
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Ans. Singleton class instance is initiated using new keyword whereas static class instance is created using static method. | ||||
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Ans. http://javasearch.buggybread.com/CodeSnippets/searchCodeSamples.php?keyword=singleton+class&category=code | ||||
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Ans. http://javasearch.buggybread.com/CodeSnippets/searchCodeSamples.php?&category=code&searchOption&keyword=964 | ||||
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Frequently asked for Lead and Architect positions. Recently asked in many US companies. | ||||
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Ans. Anti-pattern is simply the creation of a pattern in your coding that negatively affects your code i.e the Negatives surpasses the positives. | ||||
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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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Like Discuss Correct / Improve  clone  clone objects  prototype design pattern   immutable  immutability  immutability  cloning | ||||
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Ans. public class BuggyBread { | ||||
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Frequently asked Design Pattern interview question. | ||||
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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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Ans. public class SingleTon { private SingleTon() { if (singleTon != null) { throw new RuntimeException("cant not create the object"); } } public Object clone() throws CloneNotSupportedException { throw new CloneNotSupportedException("can not be create"); } static private volatile SingleTon singleTon; public static SingleTon getInstance() { SingleTon singleTon = this.sample; if (singleTon == null) { synchronized (this) { singleTon = this.singleTon; if (singleTon == null) { singleTon = this.singleton = new SingleTon(); } } } return singleTon; } } | ||||
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Ans. 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. | ||||
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Ans. Both are creational design patterns but singleton facilitates in creation and reuse of single object whereas Factory deals with creation of multiple objects. | ||||
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Ans. Factory,Abstract Factory,Singleton,Prototype and Builder | ||||
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Ans. Adapter,Bridge,Composite,Decorator,Facade,Flyweight,Proxy | ||||
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Ans. Interpreter,Chain of Responsibility,Command,Iterator,Observer,Mediator,Memento | ||||
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