1. Introduction to Java
Lecture 2
Naveen Kumar

2. Why OOP?
Modularization
 Decompose problem into smaller
subproblems that can be solved separately.
2

3. Why OOP?
Abstraction -- Understandability
 Individual modules are understandable by
human readers.
3

4. Why OOP?
 Encapsulation -- Information Hiding
 Hide complexity from the user of a software.
Protect low-level functionality.
4

5. Why OOP?
 Composability -- Structured Design
 Interfaces allow to freely combine modules to
produce new systems.
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6. Why OOP?
 Hierarchy
 Incremental development from small and
simple to more complex modules.
6
Complexity
increases

7. Why OOP?
 Continuity
 Changes and maintenance in only a few
modules does not affect the architecture.
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8. Main OOP Language Features
 Classes: Modularization, structure.
 Inheritance / extends: Hierarchy of modules,
incremental development.
 Public / Protected / Private: Encapsulation.
 Interfaces / Abstract Classes: Composability.
 Polymorphism / virtual: Hierarchy of modules,
incremental development.
 Templates: Type independent abstract data
types.8

9. Why Java ?
 Java is a general purpose object oriented
programming language
 Internet programming language
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10. Java Book’s
1. Big Java (3rd Edition)
Author : Cay Horstmann
2. The complete reference of java 2 (J2SE 6 Edition)
Author : Herbert Schieldt
3. Programming in Java2
Author : E. Balagurusamy
Web Source:
 http://java.sun.com/docs/books/tutorial/
 http://java.sun.com/javase/6/docs

11. History of Java
 A general purpose OOP language
 Developed by Sun Microsystems. (James Gostling)
 Initially called “Oak” but was renamed as “Java” in 1995
 Initial motivation is to develop a platform independent
language to create software to be embedded in various
consumer electronics devices
 Become the language of internet (portability and security)

12. Compiled and Interpreted
 Java works in two stage
– Java compiler translate the source code into byte code
– Java interpreter converts the byte code into machine level
representation
Byte Code:
-A highly optimized set of instructions to be executed by the
java runtime system, known as java virtual machine (JVM)
-Not executable code
JVM:
- Need to be implemented for each platform
- Although the details vary from machine to machine, all JVM
understand the same byte code

13.  Java compiler produces an intermediate code known as byte
code for a machine, known as JVM
 It exists only inside the computer memory
 Machine code is generated by the java interpreter by acting
as an intermediary between the virtual machine and real
machine
Java Virtual Machine
Java Program Java Compiler Bytecode
Bytecode Java Interpreter Machine Code
JVM

14. Characteristics of Java
 Java Is Simple
 Java Is Object-Oriented
 Java Is Distributed
 Java Is Interpreted
 Java Is Robust
 Java Is Secure
 Java Is Architecture-Neutral
 Java Is Portable
 Java's Performance
 Java Is Multithreaded
 Java Is Dynamic
14 www.cs.armstrong.edu/liang/intro6e/JavaCharacteristics.pdf

15. Characteristics of Java
 Java Is Simple
 Java Is Object-Oriented
 Java Is Distributed
 Java Is Interpreted
 Java Is Robust
 Java Is Secure
 Java Is Architecture-Neutral
 Java Is Portable
 Java's Performance
 Java Is Multithreaded
 Java Is Dynamic
15
Java is partially modeled on C++, but
greatly simplified and improved. It is like
C++ but with more functionality and fewer
negative aspects

16. Characteristics of Java
 Java Is Simple
 Java Is Object-Oriented
 Java Is Distributed
 Java Is Interpreted
 Java Is Robust
 Java Is Secure
 Java Is Architecture-Neutral
 Java Is Portable
 Java's Performance
 Java Is Multithreaded
 Java Is Dynamic
16
Java is inherently object-oriented. Java
was designed from the start to be
object-oriented.
One of the central issues in software
development is how to reuse code.
Object-oriented programming provides
great flexibility, modularity, clarity, and
reusability through encapsulation,
inheritance, and polymorphism.

17. Characteristics of Java
 Java Is Simple
 Java Is Object-Oriented
 Java Is Distributed
 Java Is Interpreted
 Java Is Robust
 Java Is Secure
 Java Is Architecture-Neutral
 Java Is Portable
 Java's Performance
 Java Is Multithreaded
 Java Is Dynamic
17
Distributed computing involves several
computers working together on a
network.
Java is designed to make distributed
computing (e.g. Web Services) easy.
Since networking capability is
inherently integrated into Java, writing
network programs is like sending and
receiving data to and from a file

18. Characteristics of Java
 Java Is Simple
 Java Is Object-Oriented
 Java Is Distributed
 Java Is Interpreted
 Java Is Robust
 Java Is Secure
 Java Is Architecture-Neutral
 Java Is Portable
 Java's Performance
 Java Is Multithreaded
 Java Is Dynamic
18
You need an interpreter to run Java
programs.
The programs are compiled into
bytecode. The bytecode is machine-
independent and can run on any
machine that has a Java interpreter,
which is part of the JVM