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Interview Questions and Answers - Order By Rating

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 Q751. how to access the methods of an inner class?Core Java
Ans. It depends on the type of inner class

To access non static inner class method

new OuterClass().new InnerClass().getMethod();

To access static method of static inner class

new OuterClass.InnerClass().getMethod();

  Sample Code for inner class

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   Like         Discuss         Correct / Improve     inner classes  nested aclasses     Asked in 1 Companies      Intermediate        frequent

 Q752. What is Shutdown hook ?Core Java
Ans. Shutdown hook is a thread that is invoked before the JVM is shut down. we can use it perform resource cleaning task.

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   Like         Discuss         Correct / Improve     shutdown hook  jvm
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 Q753. 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

 Q754. 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

 Q755. 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

 Q756. 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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 Q757. 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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 Q758. 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

 Q759. 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

 Q760. 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

 Q761. 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

 Q762. 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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 Q763. 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

 Q764. 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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 Q765. 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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 Q766. 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

 Q767. 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

 Q768. 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

 Q769. 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

 Q770. 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

 Q771. 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

 Q772. 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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 Q773. 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

 Q774. 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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 Q775. 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.
  Q776. 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

 Q777. 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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 Q778. 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

 Q779. Can a constructor throw an exception ?Core Java
Ans. Yes

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Frequently asked in high end product companies.
 Q780. 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

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