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These are the list of Important topics in java for Interview. You will get all the important question with there answer below. We have provided you the exact answer of each question.

  1. What is Java?

Java is a class based , Object oriented Programming Language. Java is object oriented internet Programming Language. Java Application are compiled in Bytecode which can run on Java Virtual Machine (JVM).

2. What are the Features in Java Language?

Features in Java Languages are:

Platform Independent : java Platform is independent, It is different from other Languages like C and C++. At the compilation java code in converted into byte code. Java Program can run on any machine which have JVM(Java Virtual Machine).

Multithreading : In java we can deal with many task at once define by Multithreading. Multithreading shares a Common Area.

Robust : java is a Strong Programming language which has its strong memory management.

3. What is JVM?

  • JVM(Java Virtual machine) is Runtime Environment in which Java Bytecode can be executed.
  • JVM verifies the code.
  • JVM execute the code.
  • JVM provide runtime environment.
  • JVM is a Platform dependent that is for each software and hardware we have different JVM configuration.

4. What is JRE?

  • JRE(Java Runtime Environment) is a combination of JVM & Libraries.
  • JRE is a implementation of JVM.
  • In JRE to run any Java code JRE is minimum required.
  • JRE contains set of libraries that JVM uses at runtime.
  • JRE is Platform Independent.

5. What is JDK?

  • JDK(Java Development Kit) contains JRE + libraries + Developments tools.
  • JDK is full features software developments kit.
  • JDK is a key pair platform components for Building java Applications.

6. What are the Difference between Abstract and Interface in Java?

Abstract:

  • Abstract doesn’t support multiple implementation
  • Abstract contains Data member.
  • Abstract contains Constructors.
  • In Abstract Only complete member of abstract class can be static.
  • Abstract contains Access modifiers.

Interface:

  • Interface support multiple Implementation.
  • Interface doesn’t contains Data member.
  • Interface doesn’t contains Constructors.
  • Member of Interface cannot be static.
  • Interface doesn’t support Access modifiers, It has everything by default public.

7. What are Various access Modifiers in Java?

  • Public : In public Data can be Access in same class, subclass of same package, other class in same package, subclass in other packages and non-subclass in other package.
  • Protected : In Protected Data can be Access in same class, subclass of same package, other class in same package and subclass in other packages
  • Default : In Default Data can be Access in same class, subclass of same package and other class in same package
  • Private Protected : In Private Protected Data can be Access in same class, subclass of same package and subclass in other package.
  • Private : In Private Data can be Access only in same class.

8. What is Constructor in Java?

Constructor in java is a special member of a class. Constructor in Java is used to construct or provide memory to the individuals objects.

There are two types of Constructor in Java:

  • Default Constructor : Default constructors are also known as zero parameterize Constructor . Zero parameterize constructors does not have any arguments.
  • Parametrized Constructor : Parametrized Constructor are those constructors which have some arguments. if that constructors contains one arguments then it is called as One Parametrized Constructor or if it contains two arguments then is called as Two Parametrized Constructor.

9. What is Array in Java?

Array is a collection of homogenous or similar data type. The length of array is assigned when the array is created and after creation its length is fixed. Array is always created at Runtime.

10. What is “Static” keyword is Java?

static keyword is used for declaring class attributes & behavior that is static keyword represents class. It is same to global variable of other language.

11. Why in Java main method is declare has static Keyword?

Main method has static keyword because it can be directly executed first without creating its class object.

12. What is the “This” Keyword in Java?

This is a simple member of class. It is predefined keyword used in java constructors and non static method. This keyword contains the reference of current object.

13. What is Inheritance in Java?

Inheritance in java is a mechanism in one object acquires all the properties and behavior of a parent object. In Inheritance we can built new class upon an existing class.

14. What is Type Casting in java?

Type Casting in java is also called as Type conversion. In Type casting one specific data type is converted into another specific data type variable.

There are two type of Type Casting in Java?

Up Casting: It is also called as Implicit casting. In this casting lower data type can be assign into higher data type.

ex: byte –> int –> float –> double

Down Casting : It is also called as Explicit casting. In this higher data type can be assign into lower data type.

ex: double –> float –> int –> double

15. What is “Super” is Java?

Super Keyword in used for invoking parent class properties. Constructor of parent class not inheritance in subclass.

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Author: Raiyan

Hi, I guess you're here because you want to know a bit about me. huh? I am not so good on talking about myself but I'll give a short about me.

My Name is Raiyan. I am a Professional Application Developer and a Blogger.
I started this website to Share my Knowledge. Here I provide all my knowledge whatever I earned till now.

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