Design - Interview Questions and Answers for 'Cognizant (cts)' | Search Interview Question

Design - Interview Questions and Answers for 'Cognizant (cts)' - 7 question(s) found - Order By Newest

Very Frequently asked. Have been asked in HCL Technologies very frequently ( based on 3 feedback ). Among first few questions in many interviews.

Q1. Differences between abstract class and interface ?

Core Java

Ans. Abstract classes can have both abstract methods ( method declarations ) as well as concrete methods ( inherited to the derived classes ) whereas Interfaces can only have abstract methods ( method declarations ).

A class can extend single abstract class whereas it can implement multiple interfaces.

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_{Like Discuss Correct / Improve java classes abstract class interfaces abstract class vs interface abstract classes vs interfaces Asked in 82 Companies basic frequent}

Almost sure to be asked in every company using any Dependency Injection framework ( Spring, Guice etc )

Q2. What is Dependency Injection or IOC ( Inversion of Control ) ?

Design

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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_{Like Discuss Correct / Improve design patterns ioc ( Inversion of Control ) dependency injection Asked in 83 Companies intermediate frequent}

Q3. What is the use of Transient Keyword ?

Core Java

Ans. It in Java is used to indicate that a field should not be serialized.

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Very Frequently asked to Senior Software Engineers or Developers.

Q4. Describe some of the Design Patterns you have used ?

Design

Ans. [Open Ended Answer]

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_{Like Discuss Correct / Improve design patterns Asked in 17 Companies intermediate frequent}

Q5. How to avoid cloning, serialization in the singleton class ?

Design

Ans. For Cloning-exception,For deserialization-read.resolve()

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Q6. When singleton can break and how to resolve it

Design

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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Q7. How you can check Object is created or not in case of Singleton using Object class method ?

Design

Ans. Reflections-- setAccesible--avoid using enumns

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