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Interview Questions and Answers - Order By Newest

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 Q901. What is the difference between ServletConfig and ServletContext ?Java EE
Ans. http://www.java4s.com/java-servlet-tutorials/difference-between-servletconfig-and-servletcontext-in-java/

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   Like         Discuss         Correct / Improve     ServletConfig  ServletContext     Asked in 1 Companies

 Q902. Explain some of the features of Java ?Core Java
Ans. Object Oriented - Java is object oriented but isn't purely object oriented as we have primitives along with objects.

Platform Independent - As JVM provides the translation to the Machine code as per the underlying Operating System.

Interpreted as well as compiled - Java files are compiled as class files and then class files are interpreted by JVM.

Runs on a Virtual Machine - Which is JVM that acts as an independent sub environment.

Multi-threaded - As applications can run on single thread as well as multi thread.

Modularity - Through usage of Classes , methods and Interfaces.

Robust

Usage in variety of Application types - Web , Gaming, BigData.

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 Q903. Name some of the Java Keywords ?Core Java
Ans. Static , Final , Synchronized, private , public , protected, volatile, transient, super, this,import , abstract,native,default (effective java 8), new

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   Like         Discuss         Correct / Improve     java keywords        frequent

 Q904. Which operators in Java have highest precedence ?Core Java
Ans. Braces, i.e () and [] have the highest precedence

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   Like         Discuss         Correct / Improve     java operators

  Q905. 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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   Like         Discuss         Correct / Improve     exception handling     Asked in 18 Companies      basic        frequent

 Q906. How is hashcode calculated in java ?

or

What are the rules for hashcode calculation ?		Core Java
Ans. General contract of hashCode is:

1.Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer,

2.If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.

3.It is not required that if two objects are unequal according to the equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results.

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   Like         Discuss         Correct / Improve     hashcode     Asked in 1 Companies      expert

 Q907. 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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   Like         Discuss         Correct / Improve     main method  static     Asked in 4 Companies      Basic

 Q908. 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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   Like         Discuss         Correct / Improve          Asked in 1 Companies      Basic

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 Q909. Write code for LRU CacheCore Java
Ans. https://www.geeksforgeeks.org/lru-cache-implementation/

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   Like         Discuss         Correct / Improve     cache  LRU cache  coding  code     Asked in 10 Companies      intermediate

 Q910. Can a constructor throw an exception ?Core Java
Ans. Yes

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   Like         Discuss         Correct / Improve          Asked in 1 Companies

 Q911. Can constructor be synchronized in Java ?Core Java
Ans. No, constructors can not be synchronized in Java. In fact using the keyword synchronized with a constructor results in compilation error.

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   Like         Discuss         Correct / Improve          Asked in 1 Companies      expert

 Q912. Will finally run if we have return statement and it exits the method early ?Core Java
Ans. finally will execute in all graceful situations - graceful executions as well as graceful exceptions. The only situation when finally block won't execute is when the app is abruptly stopped, killed or unplugged.

  Sample Code for finally

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   Like         Discuss         Correct / Improve     finally      Intermediate

 Q913. What are different ways for Servlet authentication ?Java EE
Ans. HTTP Basic Authentication
HTTP Digest Authentication
HTTPS Authentication
Form Based Login

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 Q914. Is it mandatory to have a default constructor ?Core Java
Ans. No.

Default constructor is provided by compiler if no constructor is provided ( argument or no argument ) by us.

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   Like         Discuss         Correct / Improve     constructor  default constructor     Asked in 1 Companies
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 Q915. 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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   Like         Discuss         Correct / Improve     environment variables  path  classpath  java_home     Asked in 3 Companies      basic        frequent

 Q916. Can an application have multiple main methods within different classes ? If yes, How will the app decide which one to be executed ?Core Java
Ans. Yes we can have a main method with string[] argument in every class of an application. When we execute an app we specify the starting point i.e the class that will get the control first and hence main method of that class gets executed.

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   Like         Discuss         Correct / Improve     main method     Asked in 3 Companies

 Q917. 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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   Like         Discuss         Correct / Improve     package   import packages     Asked in 1 Companies      basic

 Q918. What is the default value of a declared object reference ?Core Java
Ans. Null

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   Like         Discuss         Correct / Improve     object reference  null     Asked in 1 Companies      basic

 Q919. Is there a way to know size of an object in Java ?Core Java
Ans. No, Java doesn't have a sizeOf operator. In C / C++ , its required to determine how much memory allocation is required which is not the case with Java. Java handles memory allocation and deallocation intrinsically.

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   Like         Discuss         Correct / Improve     sizeOf  size of object  sizeOf operator     Asked in 1 Companies        rare

 Q920. What are the different ways to handle an exception ?Core Java
Ans. 1. Wrap the desired code in try block followed by a catch / finally to catch the exception

2. Declare the throws clause with exceptions that the code is expected to throw as an indication to the calling method to take care of it.

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   Like         Discuss         Correct / Improve     exception handling     Asked in 4 Companies
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 Q921. How does Java handle integer overflows and underflows?Core Java
Ans. It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.

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   Like         Discuss         Correct / Improve     integer  data types     Asked in 1 Companies        rare

 Q922. Is delete a keyword in Java ?Core Java
Ans. No, delete is not a keyword in Java. Destruction of objects is taken care by Java Garbage Collection mechanism.

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   Like         Discuss         Correct / Improve     delete  keywords     Asked in 1 Companies

 Q923. Is exit a keyword in Java ?Core Java
Ans. No exit is a method to exit execution of a program.

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   Like         Discuss         Correct / Improve     exit  keywords  exit a program     Asked in 1 Companies

 Q924. Who invokes a thread's run method ?Core Java
Ans. After a thread is started using a call to start method, JVM invokes the thread’s run method when the thread is initially executed.

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   Like         Discuss         Correct / Improve     threads  thread run method     Asked in 1 Companies

 Q925. What is nested interface?Core Java
Ans. Interface that is declared inside the interface or class, is known as nested interface. It is static by default.

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   Like         Discuss         Correct / Improve     interface  nested interface      intermediate
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 Q926. What kind of thread is garbage collection thread ?Core Java
Ans. Daemon thread

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   Like         Discuss         Correct / Improve     garbage collection      intermediate
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 Q927. What is the difference between the Reader/Writer java.io hierarchy and the Stream class hierarchy?Core Java
Ans. The Reader/Writer hierarchy is character oriented, whereas the Stream class hierarchy is byte oriented.

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   Like         Discuss         Correct / Improve     java io  streams      intermediate

 Q928. What is an IO Filter ?Core Java
Ans. It's an object that reads from one stream and writes to another.

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   Like         Discuss         Correct / Improve     java io  io filter      intermediate

 Q929. Can we convert a numeric IP address to a web host name ?Java EE
Ans. Yes, using InetAddress.getByName("<IP Address>").getHostName();

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   Like         Discuss         Correct / Improve     ip address to hostname  INETAddress      intermediate

 Q930. 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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   Like         Discuss         Correct / Improve     cloning  shallow copy  object cloning      basic

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