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Ans. With Java 8, We can provide method definitions in the Interfaces that gets carried down the classes implementing that interface in case they are not overridden by the Class. Keyword "default" is used to mark the default method.
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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Q44. Why do we need to specify import statement ? Don't you think Java could have been designed in such a way to automatically import everything that's in the class path ?
Ans. Java could design it in such a manner but would result in ambiguity if there are multiple files with the same name. The only way to get over it to show the message when you use any such class to provide explicit import with the package prefix. The other problem could be that Java might have to change the early import to Late import and check what's being used to decide what needs to be imported as otherwise you will see errors regarding the ambiguous imports with duplicate file name.
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Ans. Yes, to a certain extent. But the objective for Final class could be beyond just enforcing composition as certain classes might have been created without inheritance or composition in mind.
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Ans. 1. Enforcing composition over inheritance
2. Restricting overriding of certain methods
3. Final methods are faster than regular instance methods
4. Enforcing Immutability
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LikeDiscussCorrect / Improve  final class   reasons for final class   restricting inheritance  object oriented programming (oops)  oops concepts expert
Q47. What will happen if there are no interfaces in Java ?
Ans. Abstract classes can take care of that to a certain extent. Though they are little heavier than Interfaces but An abstract class with all abstract methods and no instance variables will be able to help with everything that currently an interface does.
The only problem is that a class can only extend one class whereas it can implements multiple interfaces and that is the reason Interfaces were introduced in Java, i.e to get over the problem of multiple inheritance.
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Ans. ThreadFactory is an interface that is meant for creating threads instead of explicitly creating threads by calling new Thread(). Its an object that creates new threads on demand. Using thread factories removes hardwiring of calls to new Thread, enabling applications to use special thread subclasses, priorities, etc.
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Ans. This collections class has been implemented in such a manner that it can never throw ConcurrentModificationException. As it performs update and write operations by creating a new copy of ArrayList, It's slower compared to ArrayList.
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Ans. Use Case Diagram, Component Diagram for High level Design and Class Diagram , Sequence Diagram for low level design.
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LikeDiscussCorrect / Improve  software system analyst   development lead   project lead   technical lead   technical architect expert   frequent
Frequently asked in Tata Consultancy (TCS) interview ( Based on 2 Feedback )
Ans. JIRA is written in Java and uses the Pico IOC container,Apache OFBiz entity engine, and WebWork technology stack. For remote procedure calls (RPC), JIRA supports REST, SOAP, and XML RPC.
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Ans. Everytime an object is serialized the java serialization mechanism automatically computes a hash value by passing the meta information for the class. This id is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization
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1.Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer,
2.If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
3.It is not required that if two objects are unequal according to the equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results.
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Ans. Java provides a default constructor ( no argument ) if no constructor is provided by the programmer. Java makes a check during pre compilation if there is any constructor provided by the programmer. If any constructor is provided, Java understands that programmer has provided all the mechanism for initialization and construction of the object and may not even intend to create objects by calling a no argument constructor. For example - One may like to have objects created with self defined state otherwise restrict its creation.
We make the constructor private if we want to make a class singleton as we would like to restrict creation of new objects using new operator and default constructor. Similar could be the situation wherein we would like to construct objects in a particular manner only.
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Ans. Yes , a gc method to explicitly call garbage collection immediately on the object. It will provide better flexibility over application that require optimal usage of memory.
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Q68. What are the advantage of Abstract classes over interfaces with respect to Java 7 ? and What changed in Java 8 to help facilitate that in Java 8 ?
Ans. Abstract Classes provide default implementations of methods that are inherited by the classes that extend them, which was not the case for Interfaces. This changed in Java 8, where default implementations are provided for methods.
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