Interview Questions and Answers for 'Design' | Search Interview Question

Interview Questions and Answers - Order By Newest

Q31. Why it's a good practice to expose member elements through getter methods ?

Ans. Encapsulation and Polymorphism.

We need methods to access variables in a polymorphic way as overriding only happens with methods and not with variables. Moreover getter provides a way to minimally open the access window for the object and hence provides better encapsulation. To add to those, we can have validation in the getter method before returning elements.

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Q32. What are some uses of interceptors ?

Java EE

Ans. Authentication / Authorization
URL forwarding
Auditing / Logging
Localization

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Q33. What is abstraction ?

Design

Ans. Abstraction is a process of hiding the implementation details and describing only the functionality to the user.

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Q34. What is the difference between Observer and Observable ?

RxJava

Ans. Observable is emiting data and Observer is subscribing to catch the data

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Q35. Write code to redo and undo without using system functions ?

Design

^{This question was recently asked at 'Aloha Technologies'.This question is still unanswered. Can you please provide an answer.}

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Q36. How to avoid cloning, serialization in the singleton class ?

Design

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

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Q37. 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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Q38. If you are given choice to either load object eagerly or lazily , which one would you use in case of singleton pattern ?

Design

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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Q39. Shall we use abstract classes or Interfaces in Policy / Strategy Design Pattern ?

Ans. Strategy deals only with decision making at runtime so Interfaces should be used.

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Q40. What is a Listener ?

Design

Ans. In GUI programming, an object that can be registered to be notified when events of some given type occur. The object is said to listener? for the events.

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Q41. What are use cases?

Process

Ans. It is part of the analysis of a program and describes a situation that a program might encounter and what behavior the program should exhibit in that circumstance.

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Q42. What is a Cursor ?

Database

Ans. It's a facility that allows traversal over the records pulled from a table or combination of tables. Its like iterator in Java.

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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)

Q43. Explain Singleton Design Pattern ?

Design

Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

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Q44. Shouldn't we make a class with all static members is its just expected to be executed as a standalone program with just one thread. Moreover Lets assume that there is no runtime Polymorphism required and there is no need for serialization ?

Design

Ans. Still No in case we are making use of inheritance. we may have problem wherein we have program flow moving across common inherited method and specific methods of the derived class. call made to another static method in the parent class will only access the static class of the Parent class irrespective of the call from any of the derived class.

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Q45. Give an Example for Builder Pattern ?

Core Java

Ans. String str = new StringBuilder().append("Buggy").append("Bread").toString();

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Q46. Which UML diagrams you usually use for design ?

Design

Ans. Use Case Diagram, Component Diagram for High level Design and Class Diagram , Sequence Diagram for low level design.

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Q47. What kind of software architecture your organization follow ?

Design

Ans. We have multi tier architecture with multiple layers , We have series of web servers and applications in application tier, infrastructure libraries at middle tier and Database servers at the lower tier. We are using Oracle as Database, ESB ( Enterprise service Bus ) for asynchronous communication and Rest Web Services.

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Q48. 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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Q49. What are the fail safe systems ?

Operating System

Ans. Fail Safe systems are tolerant systems that continue processing even if they sense any problem. the objective here is to continue with the processing even if there are some problems instead of completely shutting it down. Example could be to catch an exception and still letting it complete with partial results.

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Q50. Explain TDD or Test Driven Design ?

Design

Ans. TDD is a development process that involves short iterations: first an automated test case is written. Then, the code is written to pass that test, and finally one refactors the new code to acceptable standards.

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Frequently asked in face to face interviews.

Q51. Write a program to print fibonacci series.

Core Java

Ans. int count = 15;
int[] fibonacci = new int[count];
fibonacci[0] = 0;
fibonacci[1] = 1;
for(int x=2; x < count; x++){
fibonacci[x] = fibonacci[x-1] + fibonacci[x-2];
}

for(int x=0; x< count; x++){
System.out.print(fibonacci[x] + " ");
}

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Q52. Write code for singleton class

Design

Ans. http://javasearch.buggybread.com/CodeSnippets/searchCodeSamples.php?keyword=singleton+class&category=code

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Q53. Write code for the usage of Builder Design Pattern

Ans. http://javasearch.buggybread.com/CodeSnippets/searchCodeSamples.php?&category=code&searchOption&keyword=964

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Q54. What are the fail fast systems ?

Ans. Fail fast systems are intolerant systems that fails at the first instance of smelling any problem. The objective here is to break the system instead of continuing with the possibly flawed processing. Example could be breaking the processing upon an exception.

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Q55. If you are given a choice to have a functionality shared either through dependency or through a Web service, which one will you choose ?

Solution

Ans. Web Service promotes looser coupling but with comes with coding and performance overheads. Jars provide better performance and may be lesser coding but are problematic with update distribution. If the situation doesn't require frequent dependency updates and if it's only read operation of persistence, Having dependencies should be a better choice , otherwise web service.

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Frequently asked for Lead and Architect positions. Recently asked in many US companies.

Q56. What are Anti Patterns ?

Design

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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Q57. Does it make sense to clone an object which is supposed to be immutable ?

Design

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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Q58. Can Enum be a replacement for a constant file in majority of the situation ?

Design

Ans. Yes , it can be but it may not be an optimal alternative if we need to change the values frequently. As Enum is compiled like any Java File , any change requires the application to be rebuild , deployed and restart.

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Q59. Write a class explaining builder pattern ?

Design

Ans.

public class BuggyBread { 



   private String element1; 



   private String element2; 



   private BuggyBread(String element1, String element2){ 

      this.element1 = element1; 

      this.element2 = element2; 

   } 



   public static class Builder { 

    

      private String element1; 



      private String element2; 



      Builder(BuggyBread buggybread){ 

         element1 = buggybread.element1; 

         element2 = buggybread.element2; 

      } 



      Builder withElement1(String element1){ 

         this.element1 = element1; 

         return this; 

      } 



      Builder withElement2(String element2){ 

         this.element2 = element2; 

         return this; 

      } 



      BuggyBread build(){ 

         BuggyBread buggybread = new BuggyBread(element1,element2); 

         return buggybread; 

      } 

   } 

}

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Q60. Design a Library system ?

Design

Ans. Following Tables can be created

ASSET - Entity Table With foreign key reference to Table AssetType

ASSET_TYPE - Entity Table specifying information related to Asset Type like Books, CDs etc.

MEMBER - Registration information for the member

MEMBERSHIP_TYPE - Membership Types provided by Library

MEMBERSHIP - Relation table with foreign key for MEMBER ,

MEMBERSHIP_TYPE

ASSET_ISSUE_LEDGER - Relationship between MEMBER and ASSET. This specify the issue of particular asset to a particular member.

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