- Interview Questions and Answers for 'Intermediate' | 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.
Label / Company      Label / Company / Text

   



- Interview Questions and Answers for 'Intermediate' - 107 question(s) found - Order By Newest

next 30
 Q1. Why do we need Inner classes ? Cant we just work with outer classes wherever we implement Inner classes ?Core Java
Ans. Yes, we can substitute outer classes wherever we need to have inner classes but Inner classes have advantage in certain cases and hence preferred -

Ease - Why to implement a class outside if its objects are only intended to be part of an outer object. Its easy to define the class within another class if the use is only local.

Protection - Making a call an outer exposes a threat of it being used by any of the class. Why should it be made an outer class if its object should only occur as part of other objects.

For example - You may like to have an class address whose object should have a reference to city and by design thats the only use of city you have in your application. Making Address and City as outer class exposes City to any of the Class. Making it an inner class of Address will make sure that its accessed using object of Address.

  Sample Code for inner class

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

   Like         Discuss         Correct / Improve     java   inner classes   classes   objects   technical lead      intermediate
Try 1 Question(s) Test

 Q2. What are the common uses of "this" keyword in java ?Core Java
Ans. "this" keyword is a reference to the current object and can be used for following -

1. Passing itself to another method.

2. Referring to the instance variable when local variable has the same name.

3. Calling another constructor in constructor chaining.

  Sample Code for this keyword

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

   Like         Discuss         Correct / Improve     java   this   object reference   constructor chaining      intermediate        rare
Try 3 Question(s) Test

 Q3. What are the benefits of JSON over XML ?Json
Ans. Lighter and faster than XML as on-the-wire data format

Object Representation - Information is presented in object notations and hence better understandable.

Easy to parse and conversion to objects for information consumption.

Support multiple data types - JSON supports string, number, array, boolean whereas XML data are all string.

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

   Like         Discuss         Correct / Improve     json   markup language     Asked in 1 Companies      intermediate        frequent
Try 1 Question(s) Test

Frequently asked in all types of companies especially Indian Services companies. Frequently asked in CTS (Based on 2 feedback)
  Q4. What is the use of hashcode in Java ?Core Java
Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc. The value received from hashcode() is used as bucket number for storing elements. This bucket number is the address of the element inside the set/map. when you do contains() then it will take the hashcode of the element, then look for the bucket where hashcode points to and if more than 1 element is found in the same bucket (multiple objects can have the same hashcode) then it uses the equals() method to evaluate if object are equal, and then decide if contain() is true or false, or decide if element could be added in the set or not.

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

   Like         Discuss         Correct / Improve     java   collections   hashcode   advanced  hashtable     Asked in 33 Companies      intermediate        frequent
Try 1 Question(s) Test

Frequently asked in Infosys India
  Q5. What is a String Pool ?Core Java
Ans. String pool (String intern pool) is a special storage area in Java heap. When a string is created and if the string already exists in the pool, the reference of the existing string will be returned, instead of creating a new object and returning its reference.

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

   Like         Discuss         Correct / Improve     java   oops   string   string class   string pool   heap memory     Asked in 31 Companies      intermediate        frequent
Try 2 Question(s) Test

Advanced level question usually asked in High end product companies. Have been asked in Google and Amazon (Based on 1 Feedback)
  Q6. Describe, in general, how java's garbage collector works ?Core Java
Ans. The Java runtime environment deletes objects when it determines that they are no longer being used. This process is known as garbage collection. The Java runtime environment supports a garbage collector that periodically frees the memory used by objects that are no longer needed. The Java garbage collector is a mark-sweep garbage collector that scans Java dynamic memory areas for objects, marking those that are referenced. After all possible paths to objects are investigated, those objects that are not marked (i.e. are not referenced) are known to be garbage and are collected.

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

   Like         Discuss         Correct / Improve     java   garbage collection   java memory management   advanced     Asked in 21 Companies      intermediate        frequent
Try 4 Question(s) Test

Frequently asked question in companies using hibernate.
  Q7. Difference between first level and second level cache in hibernate ?Hibernate
Ans. 1. First level cache is enabled by default whereas Second level cache needs to be enabled explicitly.

2. First level Cache came with Hibernate 1.0 whereas Second level cache came with Hibernate 3.0.

3. First level Cache is Session specific whereas Second level cache is shared by sessions that is why First level cache is considered local and second level cache is considered global.

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

   Like         Discuss         Correct / Improve     hibernate   orm   hibernate cache   architecture   technical lead   first level cache vs second level cache     Asked in 18 Companies      Intermediate        frequent

 Q8. Can we use both "this()" and "super()" in a constructor ?Core Java
Ans. No, because both this and super should be the first statement.

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

   Like         Discuss         Correct / Improve     java   oops  this   super   constructor     Asked in 1 Companies      intermediate        rare
Try 2 Question(s) Test

 Q9. Why every object constructor automatically call super() in Object before its own constructors?Core Java
Ans. Derived object carries the body of its class as well as the body of the parent class. Its body ( member elements ) is initialized using its own class constructor whereas the body ( member elements ) carried from the parent class are initialized using super class constructor. So In order to initialize the elements of the parent class before its own elements are even initialized, super is called.

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

   Like         Discuss         Correct / Improve     java   oops   constructor   super   inheritance  object oriented programming (oops)  oops concepts   inheritence     Asked in 1 Companies      intermediate

Usually asked in relation to casting and ClassCastException.
 Q10. What is instanceOf operator ? Explain it's use ?Core Java
Ans. The operator instanceOf is used to verify if the specified object is the instance of specified class or interface.

Syntax if(x instanceOf ABC)

where x is an object reference and ABC could be a class name or interface name. The above statement will be true if x holds an object that is an instance of ABC or any of the child class of ABC or if x holds an object that implements ABC.

instanceOf operator is used to verify in case of downcasting. For ex -

DerivedClass extends BaseClass

x is the reference of BaseClass but holds DerivedClass object ( Polymorphism )

There is an operation that is defined in Derived Class, let's say derivedClassMethod()

We cannot call derivedClassMethod() directly using x as x is reference of BaseClass and not DerivedClass and hence can only access methods that are defined in BaseClass and overridden in derived class.

Though we can cast it to DerivedClass as following
((DerivedClass)x).derivedClassMethod();

But it may throw ClassCastException in case x doesn't hold an instance of DerivedClass at that point.

So before casting it to DerivedClass we may like to make sure that it is an instance of DerivedClass and hence won't throw ClassCastException.

So we make a check for it

if(x instanceOf DerivedClass) {
((DerivedClass)x).derivedClassMethod();
}

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

   Like         Discuss         Correct / Improve     instanceOf  instanceOf operator  Why we need instanceOf operator  use of instanceOf operator     Asked in 2 Companies      Intermediate        frequent

Frequently asked to fresh graduates.
 Q11. What is ACID ?Database
Ans. ACID stands for Atomicity, Consistency, Isolation, Durability is a set of properties of database transactions.

Atomicity means all or nothing. i.e parts of a transaction shouldn't commit if any one of them fails. Either the whole transaction should succeed or it should be complete rollback.

Consistency means that any transaction should lead database from one stabe state to another.

Isolation means that the execution of transaction results in a system state that would be obtained if transactions were executed serially.

Durability means that when a transaction is committed it forms the permanent state of database.

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

   Like         Discuss         Correct / Improve     database  acid     Asked in 7 Companies      Intermediate
Try 1 Question(s) Test

 Q12. Difference between Static and Singleton Class ?Core Java
Ans. 1. Static class is a class which cannot be instantiated and all its members are static whereas Singleton is the class that only permit creation of single object and then the object is reused.

2. As there is no object in Static class, it cannot participate in runtime Polymorphism.

3. As Static class doesnt allow creating objects and hence it cannot be serialized.

4. Static class body is initialized eagerly at application load time whereas Singleton object can be initiated eagerly using static blocks or lazily on first need.

5. Its not recommended to use pure static class as it fails to use many OOPs concepts.

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

   Like         Discuss         Correct / Improve     Static Class  Singleton  Static Class vs Singleton     Asked in 3 Companies      Intermediate        frequent

Very frequently asked in companies using SOA.
  Q13. What are RESTful Web Services ?Rest
Ans. REST or Representational State Transfer is a flexible architecture style for creating web services that recommends the following guidelines -

1. http for client server communication,
2. XML / JSON as formatiing language ,
3. Simple URI as address for the services and,
4. stateless communication.

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

   Like         Discuss         Correct / Improve     java   web services   rest   java   j2ee  architecture     Asked in 14 Companies      intermediate        frequent

 Q14. Does Constructor creates the object ?Core Java
Ans. New operator in Java creates objects. Constructor is the later step in object creation. Constructor's job is to initialize the members after the object has reserved memory for itself.

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

   Like         Discuss         Correct / Improve     java   constructor   object creation      intermediate        rare

Frequently asked question for intermediate developers. Frequently asked in HCL Technologies and EPAM.
  Q15. What is Volatile keyword used for ?Core Java
Ans. Volatile is a declaration that a variable can be accessed by multiple threads and hence shouldnt be cached.

  Sample Code for volatile

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

   Like         Discuss         Correct / Improve     java   oops   synchronization   volatile   java keywords     Asked in 42 Companies      intermediate        frequent
Try 1 Question(s) Test

Almost sure to be asked in every company using any Dependency Injection framework ( Spring, Guice etc )
  Q16. 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 83 Companies      intermediate        frequent

 Q17. What do you look for when you do code review ?Core Java
Ans. Modularity - First sign of good code is whether it has been segregated into methods and classes appropriately. I dont mind it in excess because I believe that is forward looking strategy as applications tends to expand and eventually become hard to read.

Self Explanatory - Variables and methods should be named in a way that the code should be self explanatory even without comments. Use of Constant variables to explain use of literal.

Proper Code Reuse - If there is anything being reused , it should be moved to parent classes / methods.

Proper composition calls - Composed hierarchy should not be access in just single line. One or two levels is ok but having multiple levels make it hard to read and debug.

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

   Like         Discuss         Correct / Improve     code review  clean code     Asked in 1 Companies      intermediate        frequent

Frequently asked to fresh graduates and less experienced developers.
 Q18. Explain multithreading in Java ?Core Java
Ans. 1. Multithreading provides better interaction with the user by distribution of task

2. Threads in Java appear to run concurrently, so it provides simulation for simultaneous activities.The processor runs each thread for a short time and switches among the threads to simulate sim-ultaneous execution (context-switching) and it make appears that each thread has its own processor.By using this feature, users can make it appear as if multiple tasks are occurring simultaneously when, in fact, each is running for only a brief time before the context is switched to the next thread.

3. We can do other things while waiting for slow I/O operations.In the java.iopackage, the class InputStreamhas a method, read(), that blocks until a byte is read from the stream or until an IOExceptionis thrown. The thread that executes this method cannot do anything elsewhile awaiting the arrival of another byte on the stream.

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

   Like         Discuss         Correct / Improve     java   threads   multi threading  concurrency   multithreading     Asked in 5 Companies      intermediate        frequent
Try 1 Question(s) Test

 Q19. what is the use of cookie and session ? and What is the difference between them ?Java EE
Ans. Cookie and Session are used to store the user information. Cookie stores user information on client side and Session does it on server side. Primarily, Cookies and Session are used for authentication, user preferences, and carrying information across multiple requests. Session is meant for the same purpose as the cookie does. Session does it on server side and Cookie does it on client side. One more thing that quite differentiates between Cookie and Session. Cookie is used only for storing the textual information. Session can be used to store both textual information and objects.

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

   Like         Discuss         Correct / Improve     session   session management   java   cookies   authentication   web application   ebay      intermediate

 Q20. How to implement an immutable class ?Core Java
Ans. We can make a class immutable by

1. Making all methods and variables as private.

2. Setting variables within constructor.

Public Class ImmutableClass{

private int member;
ImmutableClass(int var){
member=var;
}
}

and then we can initialize the object of the class as

ImmutableClass immutableObject = new ImmutableClass(5);

Now all members being private , you cant change the state of the object.

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

   Like         Discuss         Correct / Improve     java   oops   immutable  immutability   immutable  immutability class   technical lead     Asked in 5 Companies      intermediate        frequent
Try 2 Question(s) Test

 Q21. What things you would care about to improve the performance of Application if its identified that its DB communication that needs to be improved ?Solution
Ans. 1. Query Optimization ( Query Rewriting , Prepared Statements )

2. Restructuring Indexes.

3. DB Caching Tuning ( if using ORM )

4. Identifying the problems ( if any ) with the ORM Strategy ( If using ORM )

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

   Like         Discuss         Correct / Improve     java   db   database   hibernate   orm   at&t   overstock.com   performance improvement   architecture   technical lead   architect      intermediate

 Q22. Which elements of a class are ignored during serialization ?Core Java
Ans. 1. Objects are serialized and not classes and hence Static variables are ignored.

2. Transient is an explicit declaration to ignore the variable during serialization and hence transient instance variables are ignored too.

3. Base class instance variables if the base class hasn't been declared serializable.

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

   Like         Discuss         Correct / Improve     serialization     Asked in 1 Companies      intermediate        frequent
Try 1 Question(s) Test

 Q23. When are static variables loaded in memory ?Core Java
Ans. They are loaded at runtime when the respective Class is loaded.

  Sample Code for static variable

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

   Like         Discuss         Correct / Improve     java   oops   static   static variable   memory      intermediate

 Q24. Can we serialize static variables ?Core Java
Ans. No. Only Object and its members are serialized. Static variables are shared variables and doesn't correspond to a specific object.

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

   Like         Discuss         Correct / Improve     serialization   java   oops   static   static variables     Asked in 1 Companies      intermediate        rare
Try 2 Question(s) Test

  Q25. What is the use of Transient Keyword ?Core Java
Ans. It in Java is used to indicate that a field should not be serialized.

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

   Like         Discuss         Correct / Improve     java   oops   serialization   transient   java keywords     Asked in 39 Companies      intermediate        frequent
Try 2 Question(s) Test

Very frequently asked in phone and walk in interviews.
  Q26. What are Marker Interfaces ? Name few Java marker interfaces ?Core Java
Ans. An interface without any method declaration is called as marker interface. there are 3 in-built interfaces in JVM i.e. serializable, clonable, remote

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

   Like         Discuss         Correct / Improve     java   oops   interfaces   marker interface   serializable   clonable     Asked in 21 Companies      intermediate        frequent
Try 1 Question(s) Test

 Q27. When do you get ClassCastException?

or

What is ClassCastException ?
Ans. As we only downcast class in the hierarchy, The ClassCastException is thrown to indicate that code has attempted to cast an object to a subclass of which it is not an instance.

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

   Like         Discuss         Correct / Improve     java   oops   class casting   classcastexception   exception   error     Asked in 4 Companies      intermediate        frequent
Try 2 Question(s) Test

 Q28. what is fail fast and Fail Safe in collections?Core Java
Ans. Iterators in java are used to iterate over the Collection objects.

Fail-Fast iterators immediately throw ConcurrentModificationException if there is any addition, removal or updation of any element.

Fail-Safe iterators don't throw any exception if a collection is structurally modified while iterating over it. This is because, they operate on the clone of the collection and not on the original collection.

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

   Like         Discuss         Correct / Improve     ail fast   fail saf     Asked in 9 Companies      intermediate

 Q29. What is comparator interface used for ?Core Java
Ans. The purpose of comparator interface is to compare objects of the same class to identify the sorting order. Sorted Collection Classes ( TreeSet, TreeMap ) have been designed such to look for this method to identify the sorting order, that is why class need to implement Comparator interface to qualify its objects to be part of Sorted Collections.

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

   Like         Discuss         Correct / Improve     java   collections   treemap   treeset   comparator     Asked in 2 Companies      Intermediate
Try 2 Question(s) Test

  Q30. Can we overload main method in Java ?Core Java
Ans. Yes, but the overloaded main methods without single String[] argument doesn't get any special status by the JVM. They are just another methods that needs to be called explicitly.

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

   Like         Discuss         Correct / Improve     java   main method   overloading   yes-no     Asked in 6 Companies      intermediate        frequent

next 30

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

Any input from you will be highly appreciated and It will unlock the application for 10 more requests.

Company Name:
Questions Asked: