Core Java - Interview Questions and Answers for 'Basic' | Search Interview Question

Interview Questions and Answers - Order By Newest

Q211. What are Collection Classes ?

Ans. Collections in java is a framework of classes that provides an abstracted data structure to store and manipulate the group of objects. Each class is unique in the way it stores , search , sort and modify the elements.

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Q212. What is Maven ?

Maven

Ans. Maven is a build automation tool used primarily for Java projects.

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Q213. Which class is the root class of all Exceptions in Java ?

Ans. Throwable

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Q214. What is MAC Address ?

Networking

Ans. A media access control address is a unique identifier assigned to network interfaces for communications at the data link layer of a network segment. MAC addresses are used as a network address for most IEEE 802 network technologies, including Ethernet and Wi-Fi.

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Q215. What is an exception and exception handling in Java ?

Core Java

Ans. An Exception in java is the occurrence during computation that is anomalous and is not expected.

Exception handling is the mechanism which is used to handle such situations.

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Q216. Why main method is declared static ?

Core Java

Ans. static is the keyword that makes it accessible even without creating any object and using class name only. Making it non static would like creation of object upfront before calling the method.

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Q217. Create a Class Bank with the methods to deposit and Withdraw ?

Core Java

Ans. class Bank {
int balance;

Bank(){
balance = 0;
}

void deposit(int amount){
balance = balance amount;
}

int withdraw(int amount){
balance = balance - amount;
return balance;
}
}

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Q218. Which environment variables do we need to set in order to run Java programs?

Core Java

Ans. PATH, CLASSPATH and JAVA_HOME

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Q219. Does importing a package imports all its sub packages too ?

Core Java

Ans. No, but we can use wild card (*) to do so

For example -

import java.util.*

will import all packages with name starting with java.util

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Q220. What is the default value of a declared object reference ?

Core Java

Ans. Null

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Q221. Difference between shallow copy and object cloning ?

Core Java

Ans. Shallow copy is one of the way for object cloning, other being deep copy.

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Q222. Which Web and Application server is being used by your application ?

Server

Ans. We are using Apache 2.3 and Tomcat 5.6

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Q223. What is a class and object ?

or

How would you explain a fresher the concept of class and object in simple terms ?

Core Java

Ans. Class is a template using which objects are created in memory. It's kind of a mold using which objects with body / state are made.

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Q224. What is archiving ?

Process

Ans. It's the process of preserving the state of an object and then restoring it.

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Q225. Write any sorting algorithm.

Algorithm

Ans. https://javasearch.buggybread.com/InterviewQuestions/questionSearch.php?searchOption=label'

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Q226. What are the different primitive data types in Java ?

Core Java

Ans. boolean
byte
char
double
float
int
long
short
void

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Q227. What are the different operators in Java ?

Core Java

Ans. && - AND
|| - OR
! - LOGICAL NOT

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Q228. Write a Program to remove duplicate words from the String

Core Java

Ans.
public class BuggyBread {
public static void main(String args[]) {
String str = "we are what we repeatedly Do excellence, then, is not an act but a haBit";
Set<String> wordSet = new LinkedHashSet(); // Using Linked Hash Set as we would like to retrieve words in the insertion order

for(String word: str.split(" ")){
wordSet.add(word);
}

for(String word: wordSet){
System.out.print(word);
System.out.print(" ");
}
}
}

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Q229. What are the core OOPs concepts ?

Core Java

Ans. Abstraction, Encapsulation, Polymorphism , Composition and Inheritance

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Q230. What are some of the Java Naming conventions ?

Core Java

Ans. 1. Class name should be a noun and should start with capital case character.

2. Interface Name should be an adjective and should start with capital case character.

3. Method and Variable names should follow lower camel case notation.

4. package name should be all lower case.

5. constant variables (static final) should be all capital case.

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Q231. Write program to create a linked list and perform different operations on it.

Algorithm

Ans. import java.util.*;
class LinkedListSolution{
protected LinkedList list;
public LinkedListSolution(){
list = new LinkedList();
}
public Object pop() throws NoSuchElementException{
if(list.isEmpty())
throw new NoSuchElementException();
else
return list.removeFirst();
}
public void push(Object obj){
list.addFirst(obj);
}
public Object peek() throws NoSuchElementException{
if(list.isEmpty())
throw new NoSuchElementException();
else
return list.getFirst();
}
public boolean isEmpty(){
return list.isEmpty();
}
public String toString(){
return list.toString();
}
}
class TestStack{
public static void main(String args[]){
LinkedListSolution s = new LinkedListSolution();
s.push("First");
s.push("Second");
s.push("Third");
System.out.println("Top: " s.peek());
s.push("Fourth");
while(!(s.isEmpty()))
System.out.println(s.pop());
}
}

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Q232. What is the precedence of operators in Java ?

Core Java

Ans. http://introcs.cs.princeton.edu/java/11precedence/

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Q233. What will we get if we try to print local variable that hasn't been initialized ?

Core Java

Ans. It will print the garbage value as compiler doesn't provide a default value to local variables.

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Q234. What is JVM ?

Core Java

Ans. JVM (Java Virtual Machine) is an abstract machine. It is a specification that provides runtime environment in which java bytecode can be executed.JVMs are available for many hardware and software platforms (i.e. JVM is platform dependent).Runtime Instance Whenever you write java command on the command prompt to run the java class, an instance of JVM is createdThe JVM performs following operation:Loads codeVerifies codeExecutes codeProvides runtime environment

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Q235. What is recursion in Java ?

Core Java

Ans. It's a programming technique wherein the method can call itself. The method call usually involves a different set of parameters as otherwise it would lead to an infinite loop. There is usually a termination check and statement to finally return the control out of all function calls.

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Q236. What will happen if we don't have termination statement in recursion ?

Core Java

Ans. It would result in endless function calls and hence eventually would result in stackoverflow exception.

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Q237. What is the importance of Abstract Class ?

Core Java

Ans. Abstract classes provide a mechanism of interfacing ( using abstract method ) as well as code reuse through inheritance ( extending abstract class )

Comparing to concrete class they have an advantage of providing interface which a concrete class doesn't provide.

Comparing to interfaces they have an advantage of providing code reuse through inheritance which interfaces dont provide.

Sample Code for abstract class

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Q238. Which of the two - compile time and run time polymorphism - requires signature of the method to be different ?

Core Java

Ans. runtime polymorphism or method overriding doesn't require method name and signature to be different whereas compile time polymorphism or method overloading requires method name to be same but the signature to be different.

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Q239. Write a Program to convert a binary to number ?

Core Java

Ans. int convert(int binaryInt) {
int sumValue=0;
int multiple = 1;
while(binaryInt > 0) {
binaryDigit = binaryInt;
binaryInt = binaryInt /10;
sumValue = sumValue (binaryDigit * multiple);
multiple = multiple * 2;
}

return sumValue;
}

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Q240. What is the difference between Enumeration and Iterator ?

Core Java

Ans. Enumeration can iterate only legacy collections like Vector , HashTable and Stack whereas Iterator can iterate both legacy and non legacy collections.

Enumeration is less safer than Iterator

Enumeration is fail safe whereas Iterator is fail fast

Iterator allows for removal of element while traversal whereas Enumeration doesn't have remove method.

Enumerations were introduced in Java 1 whereas Iterators were introduced with Java 2

Enumerations have methods like hasMoreElements and nextElement whereas Iterators have methods like hasNext, next and remove

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