Interview Questions and Answers for 'Design' | Search Interview Question - javasearch.buggybread.com

Javasearch.buggybread.com

Search Interview Questions

More than 3000 questions in repository.

There are more than 900 unanswered questions.
Click here and help us by providing the answer.

Have a video suggestion.
Click Correct / Improve and please let us know.

Submit Question

Interview Questions and Answers - Order By Newest

next 30

Q11. Difference between Factory and Strategy Design Pattern ?

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}

Q12. If you are given a choice to implement the code to either Insert a Record or Update if already exist, Which approach will you follow ?

1. Insert into the DB Table. If exception occurs, update the existing record.
2. Check if the record exists and update it if it exists, If not insert a new record.

Ans. In first case, there would be 2 DB calls in worst case and 1 in best case. In 2nd approach there will be always 2 DB calls.

Decision on the approach should depend on the following considerations -

1. How costly is the call to DB ? Are we using indices , hibernate etc

If calls to DB are costly , 1st approach should be the choice.

2. Exception Book keeping load upon exception.

The benefit of saving 1st call in approach 1 should be bigger than the Book keeping for the exception.

3. Probability of the exception in first apparoach.

If the DB Table is almost empty, it makes sense to follow Approach 1 as majority of the 1st calls will pass through without exception.

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

_{Like Discuss Correct / Improve database insert-update db exceution plan db strategy design architecture technical lead}

Q13. In which cases , moving methods to utility class could be useful ?

Ans. It could be worthy to move a method to util class if the method needs to be shared, doesn't require polymorphic behavior and need not be overridden in special cases.

Don't belong to one group through is-a relationship ( You can share through parent class method )

Don't implement a specific interface ( java 8 default methods )

Doesn't involve complex computing as you will be loosing the benefit of object state with just static method.

Doesn't require polymorphic behavior as static methods don't participate in runtime polymorphism.

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

_{Like Discuss Correct / Improve utility classes util classes static methods application design rare}

Q14. What is coupling and Cohesion ?

Ans. Coupling is the degree of interdependence between software modules, a measure of how closely connected two modules are or the strength of the relationships between modules.

Cohesion refers to the degree to which the elements of a module belong together. Cohesion measures the strength of relationship between pieces of functionality within a given module.

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

_{Like Discuss Correct / Improve coupling cohesion Asked in 10 Companies frequent}

Q15. Design a Data Structure for a full text Search ?

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

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

_{Like Discuss Correct / Improve Full Text Search Data Structure Asked in 1 Companies expert}

Q16. What are the benefits of Dependency Injection or IOC ?

Ans. Central place for configuring dependencies.

No need to create object, container manage all this By using Run time polymorphism and association.

Facilities development of framework / libraries by injecting implementation classes in the implementation code.

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

_{Like Discuss Correct / Improve dependency injection IOC inversion of control}

Q17. If you need to consume messages from the queue faster, which approach will you recommend - batching or concurrency ?

Ans. Each has it's own advantages

Batching requires less resources but may result in loosing whole batch in case of failure whereas concurrency even though is little more expensive in terms of resources but would result in minimal loss in case of failure.

In case messages are to be consumed in a particular order, batching them in that order and then consuming them makes better sense.

if incoming messages are not continuous , it makes more sense to do concurrency as we need not wait for all messages to form a batch and flush. Though time sensitivity can be added but that would add unnecessary complexity.

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

_{Like Discuss Correct / Improve concurrency vs batching concurrency multithreading batch}

Q18. What is the difference between subject and observable ?

Ans. Subject has state, it keeps a list of observers. On the other hand, an Observable is really just a function that sets up observation. While Subjects are Observables, Subjects also implement an Observer interface.

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

_{Like Discuss Correct / Improve RxJava Design Design Pattern}

Q19. What are the disadvantages of Design Patterns ?

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}

Q20. What Design pattern Wrapper Classes implement ?

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}

Q21. Difference between Proxy and Adapter ?

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 proxy vs adapter expert}

Q22. Difference between Adapter and Facade ?

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}

Q23. Example of Chain of Responsibility Design Pattern ?

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}

Q24. Example of Observer Design Pattern ?

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}

Q25. What are different types of dependency injections ?

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}

Q26. What is the difference between these two approaches of creating singleton Class ?

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

//Single checked locking code
public static Singleton createInstance() {
   synchronized(Singleton.class) {
      if(singleton == null) {
         singleton = new Singleton();
      }
   }
   return singleton;
}

Ans. In First Case , Lock for the synchronized block will be received only if singleton == null whereas in second case every thread will acquire the lock before executing the code.
The problem of synchronization with singleton will only happen when the object has not be instantiated. Once instantiated , the check singleton == null will always generate true and the same object will be returned and hence no problem. First condition will make sure that synchronized access ( acquiring locks ) will only take place if the object has not been created so far.

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

_{Like Discuss Correct / Improve java singleton synchronization}

Try 1 Question(s) Test

Q27. What are design situations to use Singleton and Prototype Design Pattern ?

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

Q28. What are the advantages and disadvantages of Factory Design Pattern ?

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}

Very Frequently asked to Senior Software Engineers or Developers.

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

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 would you do an object oriented design on animals in a zoo ?

^{This question was recently asked at 'Booking.com,InterContinental Hotels,Caissa,Workday'.This question is still unanswered. Can you please provide an answer.}

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

_{Like Discuss Correct / Improve Asked in 4 Companies}

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.

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

_{Like Discuss Correct / Improve encapsulation}

Q32. What are some uses of interceptors ?

Ans. Authentication / Authorization
URL forwarding
Auditing / Logging
Localization

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

_{Like Discuss Correct / Improve interceptors interceptor design pattern}

Q33. What is abstraction ?

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

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

_{Like Discuss Correct / Improve bstraction oops concepts oops principle Asked in 22 Companies}

Q34. What is the difference between Observer and Observable ?

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

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

_{Like Discuss Correct / Improve RxJava Design Deaign Pattern}

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

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

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

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

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

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

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

_{Like Discuss Correct / Improve singleton cloneable serializable serialization cloning Asked in 1 Companies}

Q37. When singleton can break and how to resolve it

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.

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

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

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

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.

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

_{Like Discuss Correct / Improve design Pattern Singleton Lazy vs Eager Loading}

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.

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}

Q40. What is a Listener ?

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.

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

_{Like Discuss Correct / Improve java gui ui programming swing awt swt listener architecture}

next 30