Basic Java Interview Questions and answers

In this article, we will learn some Basic Java Definitions for freshers. In earlier post i have written Top 10 Job Portal websites in India. Here I am writing Introduction of java and Basic Java interview questions.

1) What is Programming Language?

Ans:  A programming Language is a formal Computer Language which is used to design instructions that are executed by a particular machine for performing some tasks
(computation evaluation etc).

2) What is POP?

Ans: POP means Procedure Oriented Programming language is which a list of instructions is given to the computer to follow, in order to perform  a task. These instructions are organized into groups which are known as functions(procedures). Examples: BASIC,BCPL,C,COBOL

3) What is OOP?

Ans: OOP means Object Oriented Programming Language is based on Objects,instead of just functions and procedures. These objects are organized into classes,which allow individual objects to be group together. Examples: C++,JAVA,C# etc..

4) What is Source Code?

Ans:  A source code is a code which is written by programmer in human readable form with proper programming syntax.

5) What is Byte Code?

Ans: Byte Code is the Intermediate code generated by the Java Compiler. Byte Code run by JVM instead of the original machine(computer processor).

6) What is Executable Code?

Ans:  It is the machine understandable code, which can be executed by a machine(OS).

7) What is API?

Ans:  API means Application Programming Interface,is an interface implemented by a software program that enables it to interact with the other software.

8) What is JDK?

ANS:  JDK means Java Development Kit, it is a set of tools which are used for developing java programs.

9) What  is JRE?

ANS: JRE means Java Runtime Environment is a collection of libraries and other components which are required to run code written in java language.

10) What is JVM?

Ans: JVM means Java Virtual Machine,is a traditional platform-independent execution environment that converts java byte code into machine code for execution.

11) What is JavaC?

Ans: JavaC means Java Compiler,which converts java source code(.java) into byte code(.class)

12) What is JCL?

Ans: Java Class Library is a set of libraries that java applications can call at run time.

13) What is Token?

Ans:  Token is a individual unit in a program. Basically they are the individual words,symbols and punctuation marks.

14) What is Constants?

Ans: Constants are the fixed values that do not changed during the execution of a program.

15) What is variable?

Ans: A variable is  a memory-location in the program's memory which is used to store data value or information. Value stored in a variable can be modified during program's execution.

16) What is Identifier?

Ans: Identifier is a tag name for a particular entity which uniquely identifies it. Example: variable,function etc..

17) What is Datatype?

Ans: Data type gives information about type-definitions that means type of data which is to be stored in a variable.

18) What are Keywords?

Ans: Keywords are the reserved words whose meaning is already known to the Compiler.

19) What are Operators?

Ans: Operators are the symbols which perform a predefined operation on operands.

20) What is Expression?

Ans: A statement having valid operators and operands sequence is known as expression.

21) What is Recursion?

Ans: When a function class itself, it is known as Recursion

22) What is class?

Ans: Class is a blue-print from which objects are created. Class contains data members to store information and member functions to operate upon data members.

23)  What is Object?

Ans: Object is an instance of a class. It is basically a real world implementation of the class having all those property values which are defined or structured in the class

24) What is Super class or Base class?

Ans:  Whose properties are inherited by another class

25)  What is derived class?

Ans:  One who inherit the properties of the base class

26) What is Inheritance?

Ans: When a class inherits or acquires the property of another class this is known as inheritance.

27) What is interface?

Ans:  Interface is a way of defining the behavior that's class can implement. It contains only abstract methods and final variables.

28) What is polymorphism?

Ans: Polymorphism means one name many forms that means one entity behaves differently in different situations.

29) What are Wrapper class?

Ans: Wrapper classes are used to convert any primitive data type into an object.

30) What is abstract class?

Ans: Abstract class is a class which can not be instantiated.