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Interview Questions and Answers for 'Wits' - 14 question(s) found - Order By Newest

Very frequently asked. Among first few questions in almost all interviews. Among Top 5 frequently asked questions. Frequently asked in Indian service companies (HCL,TCS,Infosys,Capgemini etc based on multiple feedback ) and Epam Systems
  Q1. Difference between == and .equals() ?Core Java
Ans. "equals" is the method of object class which is supposed to be overridden to check object equality, whereas "==" operator evaluate to see if the object handlers on the left and right are pointing to the same object in memory.

x.equals(y) means the references x and y are holding objects that are equal. x==y means that the references x and y have same object.

Sample code:

String x = new String("str");
String y = new String("str");

System.out.println(x == y); // prints false
System.out.println(x.equals(y)); // prints true

  Sample Code for equals

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   Like         Discuss         Correct / Improve     java   string comparison   string   object class   ==    equals   object equality  operator   == vs equals   equals vs ==     Asked in 294 Companies      basic        frequent

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  Q2. Explain OOPs

or

Explain OOPs Principles

or

Explain OOPs Concepts

or

Explain OOPs features

or

Tell me something about OOPs
Core Java
Ans. OOPs or Object Oriented Programming is a Programming model which is organized around Objects instead of processes. Instead of a process calling series of processes, this model stresses on communication between objects. Objects that all self sustained, provide security by encapsulating it's members and providing abstracted interfaces over the functions it performs. OOP's facilitate the following features

1. Inheritance for Code Reuse
2. Abstraction for modularity, maintenance and agility
3. Encapsulation for security and protection
4. Polymorphism for flexibility and interfacing

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   Like         Discuss         Correct / Improve     oops  oops features     Asked in 260 Companies      basic        frequent


Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. Frequently asked in HCL Technologies, TCS and Accenture.
  Q3. What is the difference between final, finally and finalize() ?Core Java
Ans. final - constant variable, objects cannot be de-referenced, restricting method overriding, restricting class sub classing.

finally - handles exception. The finally block is optional and provides a mechanism to clean up regardless of what happens within the try block. Use the finally block to close files or to release other system resources like database connections, statements etc.

finalize() - method helps in garbage collection. A method that is invoked before an object is discarded by the garbage collector, allowing it to clean up its state.

  Sample Code for final

  Sample Code for finally

  Sample Code for finalize

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   Like         Discuss         Correct / Improve     java   oops   final   finally   finalize   final vs finally vs finalize     Asked in 61 Companies      basic        frequent

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Basic and Very Frequently asked.
  Q4. What is Polymorphism in Java ?Core Java
Ans. Polymorphism means the condition of occurring in several different forms.

Polymorphism in Java is achieved in two manners

1. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas

2. Dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding.

  Sample Code for overloading

  Sample Code for overriding

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   Like         Discuss         Correct / Improve     polymorphism  object oriented programming (oops)  oops concepts  oops concepts     Asked in 108 Companies      Basic        frequent

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 Q5. Can you write a "Hello World" program without using any ";" within it?Core Java
Ans. Yes, That is possible

class A {
public static void main(String args[]){
if(System.out.printf("Hello World")==null){}
}
}

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   Like         Discuss         Correct / Improve     Hello World  Hello world without ;     Asked in 2 Companies        rare


  Q6. What is a self Join and give an example of a self Join ?

or

What is self Join and What is it's purpose ?
Database
Ans. When a Table Join itself , it's a Self Join. For example - we like to know the pair of department names where first dept has lesser employees than the later.

Select D1.name , D2.name from Dept D1, Dept D2 where D1.employee_count < D2.employee_count

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   Like         Discuss         Correct / Improve     sql  joins  self join  self-join  Pair of employee names with first having lesser salary than later  Pair of department names where first dept has lesser employees than the later     Asked in 26 Companies      basic        frequent


 Q7. Java doesn't provide exclusive access to memory like C/C++ and other lower level languages ? What are the advantanges and disadvantages ?Core Java
Ans. Yes, doesn't provide exclusive access as we cannot allocate and deallocate memory exclusively as Java internally manages it. The advantage of this is that it relieves the coder for such tasks and helps protect from many bugs that may get introduced with imperfect coding. Moreover as java garbage collector collects all unclaimed memory or objects, it helps the application from memory leaks.

On the flip side , as coder doesn't have extensive excess to memory , it is upto java to decide on the state for programming construct and data storage and hence may introduce some security risks. For example - Java keeps string literals in string pool and there is no exclusive way to remove it and hence may stay and sensitive data in string pool may introduce security issues. Moreover when we overwrite a value or object for a variable / reference, it is upto java to purge those values and hence it may stay in memory for a while till java decide that it is no longer referenced and hence should be removed and hence makes it vulnerable for inappropriate access.

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   Like         Discuss         Correct / Improve     disadvantages of garbage collection  advantages and disadvantages of java memory management  java for security applications  java with sensitive data  memory management


 Q8. What data type Variable can be used in a switch statement ?Core Java
Ans. Variables used in a switch statement can only be a byte, short, int, or char ( and String with Java 7 and above )

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   Like         Discuss         Correct / Improve     java   switch   variable   data type      basic        rare


 Q9. Strings in switch were introduced in Which Java version ? a. Java 5 b. Java 6 c. Java 7 d. JavaCore Java
Ans. Java 7

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   Like         Discuss         Correct / Improve     java   switch   string in switch


 Q10. Print natural numbers sequentially with two threads.Core Java
Ans. http://stackoverflow.com/questions/18799591/print-natural-sequence-with-help-of-2-threads1-is-printing-even-and-2nd-is-pri

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   Like         Discuss         Correct / Improve     print natural numbers with two threads   multithreading   multi threading   threads   code   coding   makemytrip.com


 Q11. Can I run a java program without creating any class ?
Ans. No, It requires creation of atleast one Class. Creating an object of that class is not compulsory as we can write all our logic within main method which is static.

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   Like         Discuss         Correct / Improve     java program without creating any class


 Q12. Difference between if and switch ? Can we replace all switch statements with if statements ?Core Java
Ans. if statement is used to do 2 direction branching whereas switch is used to do multi direction branching in Java.

Yes we can replace all switch statements with nested if statements.

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   Like         Discuss         Correct / Improve     switch  if vs switch


 Q13. Can we have a sub enum within an enum ?Core Java
Ans. Yes

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   Like         Discuss         Correct / Improve     enum  enum within enum


 Q14. What is context switching wrt Threads in Java?Core Java
Ans. Context Switching is the process of storing and restoring of CPU state so that Thread execution can be resumed from the same point at a later point of time.

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   Like         Discuss         Correct / Improve     Threads  multithreading  context switching



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