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Q:

What is the difference between an Interface and an Abstract class ?

Answer

1.Main difference is methods of a Java interface are implicitly abstract and cannot have implementations. A Java abstract class can have instance methods that implements a default behavior.


2.Variables declared in a Java interface is by default final. An abstract class may contain non-final variables.


3.Members of a Java interface are public by default. A Java abstract class can have the usual flavors of class members like private, protected, etc..


4.Java interface should be implemented using keyword “implements”; A Java abstract class should be extended using keyword “extends”.


5.An interface can extend another Java interface only, an abstract class can extend another Java class and implement multiple Java interfaces.


6.A Java class can implement multiple interfaces but it can extend only one abstract class.


7.Interface is absolutely abstract and cannot be instantiated; A Java abstract class also cannot be instantiated, but can be invoked if a main() exists.


8.In comparison with java abstract classes, java interfaces are slow as it requires extra indirection.

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Subject: Java

Q:

What is autoboxing and unboxing ?

Answer

Autoboxing is the automatic conversion that the Java compiler makes between the primitive types and their corresponding object wrapper classes. For example, converting an int to an Integer, a double to a Double, and so on. If the conversion goes the other way, this is called unboxing. 

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Subject: Java

Q:

Can you access non static variable in static context ?

Answer

A static variable in Java belongs to its class and its value remains the same for all its instances. A static variable is initialized when the class is loaded by the JVM. If your code tries to access a non-static variable, without any instance, the compiler will complain, because those variables are not created yet and they are not associated with any instance.

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Subject: Java

Q:

What were the most memorable accomplishments at your last job ? In your Carrer?

Answer

Focus on your most recent accomplishments, those in your current position or the job you had just prior to this one. But make sure they are relevant to the position for which you're interviewing.

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Q:

What is your Greatest Success?

Answer

This is a good question to highlight your achievements. Don't be smug or arrogant about the success of a project, especially if it was a team effort. You need to give credit to the team, too. You could say what you contributed to the total project and also give credit to others that helped in your success. Don't be overly modest, either.Here are some pointers:


1. Pick something that was clearly a success and highlight your skills.


2. Pick something recent. If you pick something twenty years ago, they are going to wonder what you have done lately.


3. Pick something important. You may have succeeded in many projects that are not that significant. 


4. Pick something easy to explain. If complicated, give the short version.


5. Be sure to explain what you learned from this success.

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Q:

What is dynamic method dispatch?

Answer

Dynamic method dispatch which is also known as runtime polymorphism is a process in which a call to an overridden method is resolved at runtime rather than at compile-time. In this process, an overridden method is called through the reference variable of a superclass. The determination of the method to be called is based on the object being referred to by the reference variable.

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Subject: Java

Q:

What is the similarity between Dynamic Binding and linking?

Answer

Dynamic binding is orthogonal to dynamic linking. Binding refers to the linking of a procedure call to the code to be executed in response to the call. Dynamic binding It is associated with polymorphism and inheritance, it(also known as late binding) means that the code associated with a given procedure call is not known until the time of the call at run-time.

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Subject: Java

Q:

What is the common usage of serialization? What exceptions occur during serialization?

Answer

The object need to be serialized when it’s sent over a network and when it’s state is saved. Exceptions which occur during serialization are:


a. transient fields


b. when the base class is serialized then only base class fields are handled.


c. static fields are ignored because they are not part of any state.

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Subject: Java