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most importent core java interview questions and answers

   Most Important Core  Java Interview Questions &  Answers for fresher and experience both


1. What is java?
A. java is object oriented programing language which is invented by james gosling in 1995. first version of java is called oak but after that its name was changed with java.



2. What are the features of java?
A. There are some features of java : 
  (a) Platform independent.
  (b) Object Oriented Programming Language.
  (c) Strongly-typed Programming Language.
  (d) Interpreted and Compiled Language.
  (e) Automatic Memory Management.

3.What is mean by Platform independent ?
A. Java is plateform independent because java uses JVM ( java virtual machine for run the 
    bytecode wich is generated by java compiler ) and JVM is plateform dependent so every
    java code after compilation it ganerates bytecode wich is pateform independent and we 
   can run this bytecode on any plateform e.i. Windows, Unix, Linux, Mac etc.



4. Why java is Object Oriented Programming Language ?
A. Java is object oriented programming language (OOP not OPPs) because every thing 
    which is present in java is in the form of object's except primitives.


5.What is Object?
A. Object is an instance of a class. When we want to access instance property of any class 
     like instance variable, instance methods then we have need of an instance(Object) of 
     any class then we have to create instance and this instance is nothing but an object.

6.What is class ?
A. A class is nothing but a block which block is define by using class keyword. Class is used 
    for defining state(data) and behaviours(methods) of an object. we can define many thing 
    inside a class like, Constructor, Methods, Block, Variables, Inner Classes, Inner Interfaces
    etc.

7. What is variables in java?
A. A variables is a name of the memory location of any data (like int a = 5; a is a variable   
     name , int is a data type, 5 is data of int type). We use variable to hold the memory  
     location of data so when we need of this data we can simply use it  by using it's name.  

8. What is Operator and what is Operands ?
A. 
      Operator :-  An Operator is a special symbol which is used to perform any kind of mathematical operations.

      Operands :- Operands are the variables which contains the data.

9. How many types of data types available in java?
A. There are two types of data types are available in java


    
10. What is JRE, JVM and JDK in java?
A.



     JVM :- Java Virtual Machine is an abstract machine for executing java byte code (byte   
                 code which is generated by java compiler). It is platform dependent.

                     
     JRE :- Java Runtime Environment is a set of  library which provides important jars, 
                interfaces and classes for execution of java program. It contains jvm inside. It is   
                platform independent.

     JDK :- Java Development Kit is a kit of development tools like Debugger, Compiler. It 
                contains JRE.
                    


























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