Design - Interview Questions and Answers for 'Pattern' | Search Java Interview Question

Design - Interview Questions and Answers for 'Pattern' - 55 question(s) found - Order By Newest

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

Q1. 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.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve design patterns ioc ( Inversion of Control ) dependency injection Asked in 80 Companies intermediate frequent}

Q2. What are the Wrapper classes available for primitive types ?

Core Java

^Anonymous

Ans. boolean - java.lang.Boolean
byte - java.lang.Byte
char - java.lang.Character
double - java.lang.Double
float - java.lang.Float
int - java.lang.Integer
long - java.lang.Long
short - java.lang.Short
void - java.lang.Void

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java5 data types wrapper classes adapter design pattern rare}

Q3. Difference between Factory and Abstract Factory Design Pattern ?

Design

^Anonymous

Ans. Factory Pattern deals with creation of objects delegated to a separate factory class whereas Abstract Factory patterns works around a super-factory which creates other factories.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java design pattern factory design pattern abstract factory design pattern technical lead expert}

Very frequently asked.Usually among first few questions.

Q4. What is MVC ?

Design

^Anonymous

Ans. MVC is a Design Pattern that facilititates loose coupling by segregating responsibilities in a Web application

1. Controller receives the requests and handles overall control of the request
2. Model holds majority of the Business logic, and
3. View comprise of the view objects and GUI component

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve j2ee mvc mvc design pattern design pattern struts spring web application web frameworks ebay Asked in 60 Companies basic frequent}

Try 1 Question(s) Test

Q5. What are the disadvantages of Design Patterns ?

Design Pattern

^{2018-06-20 12:20:03}

Ans. 1. Design patterns are abstraction heavy and hence sometimes creates memory and performance overheads.

2. Sometimes they create unnecessary complexity without much added advantage.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q6. What Design pattern Wrapper Classes implement ?

Design

^Anonymous

Ans. Adapter.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java wrapper classes adapter design pattern design pattern}

Q7. Difference between Factory and Builder Design Pattern ?

Design

^Anonymous

Ans. Builder pattern is the extension of Factory pattern wherein the Builder class builds a complex object in multiple steps.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java design pattern factory design pattern builder design pattern Asked in 1 Companies expert}

Q8. Difference between Proxy and Adapter ?

Design

^Anonymous

Ans. Adapter object has a different input than the real subject whereas Proxy object has the same input as the real subject. Proxy object is such that it should be placed as it is in place of the real subject.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java design pattern proxy adapter expert}

Q9. Difference between Adapter and Facade ?

Design

^Anonymous

Ans. The Difference between these patterns in only the intent. Adapter is used because the objects in current form cannot communicate where as in Facade , though the objects can communicate , A Facade object is placed between the client and subject to simplify the interface.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java design pattern adapter facade expert}

Q10. Difference between Builder and Composite ?

^Anonymous

Ans. Builder is a creational Design Pattern whereas Composite is a structural design pattern. Composite creates Parent - Child relations between your objects while Builder is used to create group of objects of predefined types.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java design pattern builder composite creational design pattern structural design pattern}

Q11. Example of Chain of Responsibility Design Pattern ?

^Anonymous

Ans. Exception Handling Throw mechanism.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java design pattern chain of responsibility expert}

Q12. Example of Observer Design Pattern ?

^Anonymous

Ans. Listeners.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java design pattern listeners observer design pattern expert}

Q13. Difference between Factory and Strategy Design Pattern ?

Design

^Anonymous

Ans. Factory is a creational design pattern whereas Strategy is behavioral design pattern. Factory revolves around the creation of object at runtime whereas Strategy or Policy revolves around the decision at runtime.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java design pattern factory strategy creational design pattern behavioral design pattern Asked in 1 Companies expert}

Q14. Shall we use abstract classes or Interfaces in Policy / Strategy Design Pattern ?

^Anonymous

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java design pattern strategy design patterm expert}

Q15. What are different types of dependency injections ?

Design

^{2017-11-07 09:37:47}

Ans. Setter injection
Constructor injection
Interface injection
Look-up method/method injection

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve dependency injection design patterns Asked in 1 Companies}

Q16. What's wrong with this code ?

public static void main(String[] args) {
String regex = "(\\w+)*";
String s = "Java is a programming language.";

Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(s);
while (matcher.next()) {
System.out.println("The e-mail id is: " + matcher.group());
}
}

Core Java

^{Admin
info@buggybread.com}

Ans. matcher.find() should have been used instead of matcher.next() within while.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java regex pattern.matcher java.util coding code}

Q17. Which methods of the Pattern class have equivalent methods in the String class?

Core Java

^{Admin
info@buggybread.com}

Ans. split() and macthes()

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java io string class string pattern}

Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)

Q18. Explain Singleton Design Pattern ?

Design

^{Admin
info@buggybread.com}

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java design pattern singleton at&t ebay fidelity india united healthcare india Asked in 46 Companies intermediate frequent}

Q19. Give an Example for Builder Pattern ?

Core Java

^{Admin
info@buggybread.com}

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java builder pattern design pattern stringbuilder string Asked in 3 Companies}

Try 1 Question(s) Test

Q20. 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.

^Anonymous

Ans. Singleton class instance is initiated using new keyword whereas static class instance is created using static method.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops singleton design pattern static class}

Q21. Write code for singleton class

Design

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

Help us improve. Please let us know the company, where you were asked this question :

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

Q22. Write code for the usage of Builder Design Pattern

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

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve builder design pattern builder pattern code coding intermediate}

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

Q23. What are Anti Patterns ?

Design

^{2016-07-14 14:21:11}

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.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve anti patterns design patterns Asked in 9 Companies frequent}

Q24. What are design situations to use Singleton and Prototype Design Pattern ?

Design

^{2016-07-28 20:28:43}

Ans. Both are creational design patterns.

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.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve design pattern singleton prototype creational design pattrn Asked in 7 Companies expert}

Try 1 Question(s) Test

Q25. Does it make sense to clone an object which is supposed to be immutable ?

Design

^{2016-07-28 20:54:59}

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.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve clone clone objects prototype design pattern immutable immutability immutability cloning}

Q26. Write a class explaining builder pattern ?

Design

^{2016-08-17 10:32:03}

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; 

      } 

   } 

}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve builder pattern builder class}

Try 1 Question(s) Test

Q27. What are the advantages and disadvantages of Factory Design Pattern ?

Design

^{2016-09-07 09:19:26}

Ans. Object Oriented Design Patterns is the science of identifying the pattern to make objects communicate in a way to effectively implement a Solution.

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.

Advantage of Factory Pattern - Loose Coupling and Segregation of Responsibilities. Now instead of hard binding the complete logic to decide the nature and shape of the object on the basis of some conditions, you are assigning the responsibility to some other object and hence making the relationship loosely coupled and hence main tenable.

Disadvantages - Before Understanding the Dis-advantages , we should understand that these patterns were chosen after a period of evolution and research and almost best fit for the required solution, otherwise these patterns would have easily been replaced by now.

Though the advantages of these pattern surpass the disadvantages keeping in mind the decreasing cost of resources and increasing scale of applications, but still loose coupling by means of additional objects results in decreased performance.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve factory design pattern design pattern}

Frequently asked Design Pattern interview question.

Q28. What is a prototype design pattern ?

Design

^{2016-11-04 08:06:01}

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.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve design pattern prototype design pattern cloning Asked in 11 Companies intermediate}

Very Frequently asked to Senior Software Engineers or Developers.

Q29. Describe some of the Design Patterns you have used ?

Design

^{2016-12-01 16:31:17}

Ans. [Open Ended Answer]

Help us improve. Please let us know the company, where you were asked this question :

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

Q30. How to make sure that only one instance is created in Singleton Pattern ?

Core Java

^{2016-12-21 10:00:04}

Ans. By Using Double Checked Locking code

//Double Checked Locking Code
public static Singleton createInstance() {
if(singleton == null){
synchronized(Singleton.class) {
if(singleton == null) {
singleton = new Singleton();
}
}
}
return singleton;
}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve singleton design pattern Asked in 2 Companies}

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.