Core Java Interview Questions
Questions Answers Views Company eMail

What is garbage collection in Java, and how can it be used ?

Infosys, HCL, Accenture, Wipro, Sara, SITS, TCS,

32 56337

Differentiate Vector and ArrayList?

Wipro, Max Telecom,

6 7657

Differentiate constructor and a method and how are it be used?

Wipro,

7 8197




What is an abstract class?

Wipro,

7 6974

How can final class be used?

Wipro, Accenture,

5 8880

By what default value is an object reference declared as an instance variable?

Wipro,

1 10274

Java support what type of parameter passing ?

Wipro,

7 11522

Explain the term serialization?

Wipro,

10 9324




Is there is any error if you have multiple main methods in the same class?

Wipro, Infosys,

10 10713

What is Overriding and how can it be used?

Consagous, Wipro,

7 13171

Explain pass by reference and pass by value?

IBM, Wipro,

8 11541

In which way does a Primitive data type is passed ?

Sun Microsystems,

5 7400

What happens when a main method is declared as private?

L&T, DELL, Infosys, Sun Microsystems,

22 35541

Is there any need to import java.lang package?

Sun Microsystems,

13 14742

What is UNICODE?

3 4296


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Un-Answered Questions { Core Java }

Can you give names of Container classes?

1136


when to use ArrayList and when to use HashMap in webApplication.

2734


explain the concept of virtual method invocation in polymorphism in detail?

1035


Can we call virtual funciton in a constructor ?

1045


Name the components that are termed to be Heavy-weight component but available in Light-weight components?

1338






how a programmer confirms that the data submitted has been succesfully inserted into the database(either oracle or my sql).. How a programmer confirm if there is any problem with the program he wrote for insertion... ANS:--- >executeupdate method is having boolean return type, if anything goes wrong in data insertion or data updation, it would return false. otherwise, if it successfully inserts data into the database, it would return true NOW HOW TO I CHECK IN MY DURING EXECUTION WHETHER IT RETURNS TRUE OR FALSE... WELL IT WILL DISPLAY ANY MESSAGE OR NOT

978


Highest level event class of the event-delegation model?

1689


Where will it be used?

657


What is the java project architecture?

1071


how can i use a nonsynchronized hashtable?

1345


can any body body expalin best definitions & best real time exaples for opps concepts.

1015


What are invisible components?.

980


Say you want to store the information about a number of pets in an array. Typical information that you could store for each pet (where relevant) would be • Breed of animal • Animal's name • Its birth date • Its sex • Whether it has been sterilised or not • When it is due for its next inoculation • When it last had its wings clipped For each type of pet (eg. dog, cat or bird) you would typically define a class to hold the relevant data. Note: You do not need to implement these classes. Just answer the following questions. 3.1.1 What would be the advantage of creating a superclass (eg. Pet) and declaring an array of Pet objects over simply using an array of Objects, storing each of the instances of the different pet classes (eg. Dog, Cat or Bird) in it? 3.1.2 Would you define Pet as a class or as an interface? Why? (2) (2)

630


If goto and const is reserve words than why it is not work in java?

807


Tell me about your ability to work under pressure

1008