Java is a general-purpose, platform-independent programming language designed to let developers write code once and run it anywhere. Key features include simplicity, security, portability, and robustness, with applications compiled into platform-independent bytecode executed by the Java Virtual Machine (JVM). Java supports both applications and applets for web deployment, distinguishing itself with concepts like multithreading and dynamic libraries.

1. Course Title: Programming with Java

2. What is Java?
• Java is a general-purpose computer programming
language that is concurrent, class-based, object-
oriented, and specifically designed to have as few
implementation dependencies as possible.
• It is intended to let application developers "write once,
run anywhere" (WORA), meaning that compiled Java
code can run on all platforms that support Java without
the need for recompilation.
• Java applications are typically compiled to bytecode
that can run on any Java virtual machine (JVM)
regardless of computer architecture.

3. Major features
• Designed by : James Gosling and Sun
Microsystems. The language was initially called
Oak after an oak tree .
• Developer : Oracle Corporation
• Stable release : Java Standard Edition 8 Update
60 (1.8.0_60) / August 18, 2015
• Implementation language: C and C++
• OS : Cross-platform (multi-platform)
• Filename extensions: .java , .class, .jar (Java
Archive)

4. WORA/ WORE
• "Write once, run anywhere" (WORA), or sometimes
write once, run everywhere (WORE)
• Ideally, this means Java can be developed on any
device, compiled into a standard bytecode and be
expected to run on any device equipped with a Java
virtual machine (JVM).
• The installation of a JVM or Java interpreter on chips,
devices or software packages has become an industry
standard practice.
• This means a programmer can develop code on a PC
and can expect it to run on Java enabled cell phones, as
well as on routers and mainframes equipped with Java,
without any adjustments.

5. What is Bytecode in Java ?
• Bytecode is nothing but the intermediate representation of
Java source code which is produced by the Java compiler by
compiling that source code.
• This byte code is an machine independent code.
• It is not completely a compiled code but it is an
intermediate code somewhere in the middle which is later
interpreted and executed by JVM.
• Bytecode is a machine code for JVM.
• But the machine code is platform specific whereas
bytecode is platform independent that is the main
difference between them.
• It is stored in .class file which is created after compiling the
source code.

6. What is Bytecode in Java ?

7. Java applet
• An applet is a special kind of Java program that is
designed to be transmitted over the internet and
automatically executed by a Java compatible web
browser.
• A Java applet is a small application which is
written in Java and delivered to users in the form
of bytecode.
• The user launches the Java applet from a web
page, and the applet is then executed within a
Java Virtual Machine (JVM) in a process separate
from the web browser itself.

8. Java applet
• A Java applet can appear in a frame of the web
page, a new application window, Sun's
AppletViewer, or a stand-alone tool for testing
applets. Java applets were introduced in the first
version of the Java language, which was released
in 1995.
• Java applets can be written in any programming
language that compiles to Java bytecode. They
are usually written in Java, but other languages
such as Jython,JRuby,Pascal,Scala, or Eiffel (via
SmartEiffel) may be used as well.

9. Principles
There were five primary goals in the creation of the
Java language:
• It must be "simple, object-oriented, and familiar".
• It must be "robust and secure".
• It must be "architecture-neutral and portable".
• It must execute with "high performance".
• It must be "interpreted, threaded, and dynamic".

10. Java Buzzwords
• Simple
• Secure
• Portable
• Object oriented
• Robust
• Multithreaded
• Architecture neutral
• Interpreted
• High performance
• Distributed
• Dynamic

11. Java Buzzwords
• Simple:
•Easy to learn
•Easy to write programs using Java
•More expressive.
•Most of the complex or confusing features in
C++ are removed in Java like pointers etc..

12. Java Buzzwords
• Secure:
•Java provides data security through
encapsulation.
•Also we can write applets in Java which provides
security.
•An applet is a small program which can be
downloaded from one computer to another
automatically.
•There is no need to worry about applets
accessing the system resources which may
compromise security.

13. Java Buzzwords
• Portable:
•Applications written using Java are portable
in the sense that they can be executed on any
kind of computer containing any CPU or any
operating system.
•When an application written in Java is
compiled, it generates an intermediate code
file called as “bytecode”.
•Bytecode helps Java to achieve portability.

14. Java Buzzwords
• Object - Oriented:
•Java follows object oriented model.
•So, it supports all the features of object
oriented model like:
Encapsulation
Inheritance
Polymorphism
Abstraction

15. Java Buzzwords
• Robust:
•A program or an application is said to be
robust(reliable) when it is able to give some
response in any kind of context.
•Some of those features are:
1. Type checking
2. Exception handling

16. Java Buzzwords
• Multithreaded:
•Java supports multithreading which is not
supported by C and C++.
•A thread is a light weight process.
•Multithreading increases CPU efficiency.
•A program can be divided into several threads
and each thread can be executed concurrently or
in parallel with the other threads.
•Real world example for multithreading is
computer. While we are listening to music, at
the same time we can write in a word document
or play a game.

17. Java Buzzwords
• Architecture - Neutral:
•Bytecode helps Java to achieve portability.
•Bytecode can be executed on computers
having any kind of operating system or any
kind of CPU.
•Since Java applications can run on any kind of
CPU, Java is architecture – neutral.

18. Java Buzzwords
• Interpreted and High Performance:
•In Java 1.0 version there is an interpreter for
executing the bytecode. As interpreter is quite
slow when compared to a compiler, java
programs used to execute slowly.
•After Java 1.0 version the interpreter was
replaced with JIT(Just-In-Time) compiler.
•This enhances the program performance
means it executes rapidly.

19. Java Buzzwords
• Distributed:
•Java supports distributed computation using
Remote Method Invocation (RMI) concept.
•The server and client(s) can communicate
with one another and the computations can
be divided among several computers which
makes the programs to execute rapidly.
•In distributed systems, resources are shared.

20. Java Buzzwords
• Dynamic:
•The Java Virtual Machine(JVM) maintains a
lot of runtime information about the program
and the objects in the program.
•Libraries are dynamically linked during
runtime.
•So, even if you make dynamic changes to
pieces of code, the program is not effected.

21. How Java achieved Platform
Independency ?

22. How Java achieved Platform
Independency ?
• Java achieved platform independency by
moving machine language generation from
compilation phase to execution phase by
introducing bytecodes and JVM.

23. How Java achieved Platform
Independency ?

24. How Java achieved Platform
Independency ?

25. What is the most important feature of
Java?
• Java is a platform independent language. This
is most important feature of Java language.
Platform independent language means
programs written in Java will work on any
computer that has Java installed on it,
regardless of operating system.
• Whereas Multithreading, AWT and Event
Handling, Networking, Database Connection
are important features of java.

26. Types of Java Software
• Java software is divided into two sub products
• 1) jdk (Java Development Kit)
• 2) jre (Java Run time Environment)
• jdk has both "Compiler + JVM"
• jre has only "JVM"
• JVM is a sub-part of jre and jre is a sub-part of jdk. So
in order to run any java application jre software is
sufficient but if we need to compile and execute the
java program we have to install jdk software.

27. Types of Java Software
This diagram shows the difference between jdk,jre and JVM.

28. Thanks for your patience.