The document provides an introduction to Java programming including: - Java is an object-oriented language where programs are written as classes and allows "write once, run anywhere" functionality. - Key features of Java include being simple, robust, secure, multi-threaded, and dynamically flexible. - The Java architecture includes the compiler, JVM, JRE and JDK which work together to compile and execute Java code. - Common Java applications include mobile apps, desktop apps, web apps, games, cloud apps, and IoT apps. - A basic Java program structure includes documentation, packages, imports, classes, and a main method.

1. Unit 1
Introduction to Java

2. What is Object-Oriented Programming?
• Object-oriented programming (OOP) is a programming
standard based on the concept of “objects”.
• These objects can contain data known as attributes and code
known as methods.
• The core concept of the object-oriented approach is to break
complex problems into smaller objects.

3. Introduction to Java
• Java is object-oriented programming language where
programs are written using classes.
• It allows application developers to write once, and run
anywhere (WORA)
• This means that compiled Java code can run on all platforms
that support Java without the need for recompilation.
• Java is widely used for developing applications for desktop,
web, and mobile devices.
• Java is simple, robust, and secure.

4. Explain Java Features
1. Simple, easy and familiar :
– Java is easy to learn because its syntax is just like c++.
– It is simple because it does not use header files and does not use
pointers
2. Compiled and Interpreted :
– Java code is translated into byte code after compilation and the byte
code is interpreted by JVM (Java Virtual Machine).
3. Platform Independent :
– Compiler converts source code to bytecode and then the JVM executes
the bytecode generated by the compiler.
– This bytecode can run on any platform like Windows, Linux, or macOS
which means if we compile a program on Windows, then we can run it
on Linux and vice versa.
4. Object-Oriented :
– Java is Object oriented - which means no coding outside of class
definitions, including main().
5. Robust :
– Robust means inbuilt capabilities to handle errors/exceptions.

5. 6. Secure :
– it enables to develop virus-free systems.
– It has strong authentication techniques .
7. Multithreaded :
– It is possible to write a single program that can perform many tasks
simultaneously.
8. Dynamic flexibility :
– Java gives us the flexibility to add classes, new methods to existing
classes, and even create new classes through sub-classes.

6. What is Java Architecture. Explain
• Java Architecture is a collection of components JVM,
JRE, and JDK.
• Java Architecture explains each and every step of how a java
program is compiled and executed.
• Java Architecture can be explained by using the following
steps:
– There is a process of compilation and interpretation in Java.
– Java compiler converts the Java code into byte code.
– After that, the JVM converts the byte code into machine code.
– The machine code is then executed by the machine.

7. Java Architecture

8. Java Virtual Machine
• The main feature of Java is Write Once Run Anywhere.
• Java Virtual Machine makes it possible to write our code once
and use it on any operating system.
• JVM converts byte code into machine code.
• It loads the code into memory, verifies it and then executes
the code

9. Java Runtime Environment and Java Development Kit
• The JRE contains libraries and software needed by your Java
programs to run.
• JRE takes our Java code, uses the required libraries, and
then starts the JVM to execute it.
• JDK is a software development environment used in the
development of Java applications and applets.
• Java Development Kit contains JRE, a compiler, an interpreter
, and many development tools in it.

10. List Java Applications
• Mobile App Development :
– The Java programming language is used for building android applications .
• Eg. Spotify and Twitter
• Desktop GUI Applications :
– Java provides tools which contain pre-assembled components for developing
the GUI based desktop application.
• Web-based Applications :
– Java is used for developing the web-based application using Servlet and JSP.
• Gaming Applications :
– Java is widely used for developing gaming applications
– Eg. Minecraft, Mission Impossible III, etc.

11. • Cloud-based Applications :
– Java provides the environment to develop cloud-based applications
– The cloud applications are widely used to share data between companies or to
develop applications remotely.
• IoT Applications :
– IoT is found almost in all the small devices such as smartphones, wearables,
smart lighting, TVs, etc.
– For developing the IoT application Java is used, because of its security,
flexibility, and versatility.

12. Describe structure of Java program
A Java program involves the following sections:
• Documentation Section
• Package Statement
• Import Statements
• Interface Statement
• Class Definition
• Main Method Class
– Main Method Definition

13. • Documentation Section Comments can be written in this
section. They help the programmer to understand the code.
These are optional
• Package statement A package is a group of classes that are
defined by a name. If it is required to declare many classes
within one element, it can be declared within a package. It is
an optional part of the program. package keyword is used to
create a a package. Eg. package program;
• Import statement This statement is used if it is required to
use a class of another package by specifying the package
name and the class name separated with a dot operator.
Eg. import calc.add;
• Interface statement Interfaces are like a class that includes a
group of method declarations. It's an optional section and can
be used when programmers want to implement multiple
inheritances in a program.

14. • Class Definition A Java program may contain several class
definitions. Classes are the essential elements of any Java
program.
• Main Method Class Every Java program requires the main
method, which is the starting point of the program. There may
be many classes in a Java program, but, only one class
defines the main method. Methods contain data type
declaration and executable statements.

15. A Simple Java Program
//First Java program single line comment
public class Hello
{
/* Description: multi line comment
Writes the words "Hello Java" on the screen */
public static void main(String[] args)
{
System.out.println("Hello Java");
}
}
Note:
Class name : Hello
Keywords : public, static, void
Data type : String
Array name : args

16. Write steps for Compiling and Executing a Java program taking an
example of a simple Java program
Steps to save the file, compile, and execute the program.
• Open notepad and add the Java code.
• Save the file as: Hello.java.
• Open a command prompt window and go to the directory
where you saved the java code.
• Type javac Hello.java and press enter to compile your code.
If there are no errors in your code, the command prompt will
take you to the next line.
• Now, type java Hello to run your program.
• You will be able to see Hello Java printed on the screen.