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Q41. What are use cases?

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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_{Like Discuss Correct / Improve use cases design high level design testing test driven development software system analyst project lead basic frequent}

Q42. What is a Cursor ?

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 ?

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 ?

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 ?

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

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Q46. Which UML diagrams you usually use for 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 ?

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 ?

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.

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

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

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_{Like Discuss Correct / Improve singleton code coding design pattern Asked in 1 Companies Intermediate frequent}

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 ?

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 ?

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 ?

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 ?

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 ?

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 ?

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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Frequently asked Design Pattern interview question.

Q61. What is a prototype design pattern ?

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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Q62. What are the advantages disadvantages of keeping config entries in database instead of property file and vice versa ?

Ans. Entries in DB will be retrieved at runtime unless a cache is maintained in application. Entries in File will be loaded to memory by default. Both can be implemented in 1 manner or other. By default property file will take space in memory, will be faster, and will require application restart on change. By Default DB config will be pulled at runtime, will be little slower, and doesn't require an application restart.

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Q63. Have you ever felt the need of keeping the constructor private ?

Ans. Yes, When either we don't want an object to be created ( class having all static elements and hence not required ) or object to be created using a static method or static block. One such example could be a situation when we would like app to load objects at start up and we would like to restrict new object creation by any request.

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Q64. Is it a Good practice to have application decision making in DAOs ?

Ans. No, DAO's should only have methods to perform CRUD operations. Application logic should reside in service methods.

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Q65. Can you please provide an implementation of application level cache ?

Ans. We can use an expiration map whose entries gets expired after a certain interval and then we can put the logic to retrieve the entries if its expired in map. Alternatively we can create a separate class and make map its element. We can refresh the map in this class periodically by using a monitoring thread within static block.

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Q66. What is a responsive web design ?

Ans. Responsive web design is a approach to web design that allow desktop webpages to be viewed perfectly in different devices and sizes.

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Q67. Design an online shopping site system ?

Ans. AWS Services - CloudFront for distribution / caching, EC2 for computing, EBS for block storage , S3 for object storage , RDS for database , Kinesis for streaming , CloudWatch for monitoring.

Technologies - Java for back end with Spring Boot , Angular , RxJs for front end .

Architecture - Service Oriented. Multi layer.

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Q68. Implement an LRU Cache ?

Ans. https://www.programcreek.com/2013/03/leetcode-lru-cache-java/

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Q69. How to make sure that only one instance is created in Singleton Pattern ?

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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Q70. What is a factory design pattern ?

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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