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Interview Questions and Answers - Order By Rating

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 Q821. 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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 Q822. 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

 Q823. 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

 Q824. 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

 Q825. 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

 Q826. 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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 Q827. 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

 Q828. Can we declare static variables as transient ?Core Java
Ans. It's weird that compiler doesn't complain if we declare transient with static variable because it makes no sense. At least a warning message saying "transient is useless in this situation" would have helped with code cleaning.

Static variables are never serialized and transient is an indication that the specified variable shouldn't be serialized so its kind of double enforcement not to serialize.

It could be that as it makes no different to the variable behavior and hence using both keywords with a variable are permitted.

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   Like         Discuss         Correct / Improve     static  transient  serialization     Asked in 1 Companies      expert        rare
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 Q829. 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.

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   Like         Discuss         Correct / Improve     serialization     Asked in 1 Companies      intermediate        frequent
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 Q830. 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

 Q831. Is it a good practice to use Asterick(*) in import statement to load multiple packages with single import statement ?Core Java
Ans. No, we should be lean in loading only packages which are required. Loading packages which are not being used result in memory overheads.

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   Like         Discuss         Correct / Improve     import  import packages     Asked in 1 Companies

 Q832. 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

 Q833. Can we have multiple main methods in a single class ?Core Java
Ans. We can overload the main method by specifying different argument types. For example -

2 main methods with different arguments is perfectly legal

public static void main();
public static void main(String[] args);

The following are not legal as compiler will complain of duplicate methods

public static void main(String[] args);
public static void main(String[] args);

Even The following are not legal as we cannot overload on return types

public static String main(String[] args);
public static void main(String[] args);

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   Like         Discuss         Correct / Improve     main method     Asked in 2 Companies

 Q834. 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

 Q835. 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

 Q836. 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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 Q837. Trim a string without using String library methodCore Java
 This question was recently asked at 'Ariba'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     code  coding.string  trim a string     Asked in 1 Companies

 Q838. 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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 Q839. Design an app to find 10 most visited urlsCore Java
 This question was recently asked at 'Wayfair'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve          Asked in 1 Companies

 Q840. 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

Very frequently asked. Usually asked in this format or as difference with interfaces / concrete classes.
  Q841. What is an abstract class ?Core Java
Ans. Abstract class is the class that is not supposed to be instantiated. The purpose of the class to only have extension to the derived class.

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   Like         Discuss         Correct / Improve     abstract class     Asked in 6 Companies      basic        frequent

 Q842. What will be the output of following code

public class BuggyBread {
   static class A {
      A() {
         f();
      }

      public void f() {
         System.out.println("A ctor");
      }
   }

   static class B extends A {
      B() {
         f();
      }

      public void f() {
         System.out.println("B ctor");
      }
   }

   public static void main(String[] args) {
      B b = new B();
      b.f();
      A a = new A();
      a.f();
   }
}		Core Java
Ans. B ctor
B ctor
B ctor
A ctor
A ctor

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 Q843. 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

 Q844. Can a constructor throw an exception ?Core Java
Ans. Yes

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Frequently asked in high end product companies.
 Q845. 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

 Q846. 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

 Q847. 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

 Q848. What is the use of static keyword in Java ?Core Java
Ans. static keyword is used to specify that the respective programming construct ( method , variable ) belongs to the class and not to its instance and is supposed to be shared by all instances of the class.

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   Like         Discuss         Correct / Improve     static keyword     Asked in 1 Companies      basic        frequent

 Q849. 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

  Q850. 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

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