Java - OOPS and Java Basics

OOPS and JAVA
Dr. P. Victer Paul, Indian Institute of Information Technology Kottayam 1

Programming Language
 A programming language is a computer language
programmers use to develop applications, scripts, or
other set of instructions for a computer to perform
specific tasks.
 The commonly used programming methodologies are:
 Procedural programming
 Object-oriented programming (OOP)

Procedural programming
 Involves dividing a large program into a set of sub-
procedures or subprograms that perform specific tasks.
 Module consists of single or multiple procedures.
 Most of the data is shared as global that can be accessed
from anywhere within the program.

Procedural programming

Difficulties in Procedural App
 Focus is on procedures
 All data is shared: no protection
 More difficult to modify
 Hard to manage complexity

Object Oriented programming
 an approach that provides a way of modularizing
programs by creating partitioned memory area for
both data and functions that can be used as template
for creating copies of such modules on demand.

Advantages of OOP
 Real-world programming
 Reusability of code
 Modularity of code
 Resilience to change
 Information hiding

Procedural vs. Object-Oriented
 Procedural
Withdraw, deposit, transfer
 Object Oriented
Customer, money, account

Procedural vs. Object-Oriented
S. No Procedural Programming Object-Oriented Programming
1 Emphasis on Procedures Emphasis on Data
2 Data is not hidden Data is hidden
3 Data and methods are separate Data and methods are combined using
objects
4 Data can be accessed by external
functions
Data cannot be accessed by external
functions
5 Top-down Approach in program
design
Bottom-up Approach in program
design
6 Eg. C, PASCAL Eg. C++, JAVA, Smalltalk

OOP Concepts
 Objects
 Classes
 Data Abstraction
 Data Encapsulation
 Inheritance
 Polymorphism

JAVA
 James Gosling and Sun Microsystems
 Oak
 Java, May 20, 1995, Sun World
 HotJava
 The first Java-enabled Web browser

JAVA
 James Gosling, Mike Sheridan, and Patrick
Naughton initiated the Java language project in
June 1991. The small team of sun engineers
called Green Team.
 Originally designed for small, embedded
systems in electronic appliances like set-top
boxes.
 Firstly, it was called “Greentalk” by James
Gosling, and file extension was .gt.
 After that, it was called Oak and was
developed as a part of the Green project.

JAVA
 According to James Gosling, “Java was one of the
top choices along with Silk“.
 Java is an island of Indonesia where first coffee was
produced (called java coffee).
 Notice that Java is just a name, not an acronym.
 In 1995, Time magazine called Java one of the Ten
Best Products of 1995.

Java Milestones
Year Development
1990 Sun decided to developed special software that could be used
for electronic devices. A project called Green Project created
and headed by James Gosling.
1991 Explored possibility of using C++, with some updates
announced a new language named “Oak”
1992 The team demonstrated the application of their new language
to control a list of home appliances using a hand held device.
1993 The World Wide Web appeared on the Internet and
transformed the text-based interface to a graphical rich
environment. The team developed Web applets (time
programs) that could run on all types of computers connected
to the Internet.
Dr. P. Victer Paul, Indian Institute of Information Technology Kottayam

Java Milestones
Year Development
1994 The team developed a new Web browsed called “Hot Java” to
locate and run Applets. HotJava gained instance success.
1995 Oak was renamed to Java, as it did not survive “legal”
registration. Many companies such as Netscape and
Microsoft announced their support for Java
1996 Java established itself it self as both 1. “the language for
Internet programming” 2. a general purpose OO language.
1997- A class libraries, Community effort and standardization,
Enterprise Java, Clustering, etc..

Sun white paper defines Java as:
 Simple and Powerful
 Safe
 Object Oriented
 Robust
 Architecture Neutral and Portable
 Interpreted and High Performance
 Threaded
 Dynamic

Java Attributes
 Familiar, Simple, Small
 Compiled and Interpreted
 Platform-Independent and Portable
 Object-Oriented
 Robust and Secure
 Distributed
 Multithreaded and Interactive
 High Performance
 Dynamic and Extensible

Overlap of C, C++, and Java
C
C++
Java

Java better than C++ ?
 No Typedefs, Defines, or Preprocessor
 No Global Variables
 No Pointers
 No Unsafe Structures
 No Multiple Inheritance
 No Operator Overloading
 No Automatic Coercions
 No Fragile Data Types

Object Oriented Languages -A Comparison
Feature C++ Objective C Ada Java
Encapsulation Yes Yes Yes Yes
Inheritance Yes Yes No Yes
Multiple Inherit. Yes Yes No No
Polymorphism Yes Yes Yes Yes
Binding (Early or Late) Both Both Early Late
Concurrency Poor Poor Difficult Yes
Garbage Collection No Yes No Yes
Genericity Yes No Yes Limited
Class Libraries Yes Yes Limited Yes

JDK Editions
 Java Standard Edition (J2SE)
 J2SE can be used to develop client-side standalone
applications or applets.
 Java Enterprise Edition (J2EE)
 J2EE can be used to develop server-side
applications such as Java servlets and Java
ServerPages.
 Java Micro Edition (J2ME).
 J2ME can be used to develop applications for
mobile devices such as cell phones.

JDK
 Versions
 JDK 1 (1995), JDK 1.2 (1998), JDK 1.3 (2000)
 JDK 1.4 (2002), JDK 1.5 (2004), JDK 6 (2006)
 JDK 7 (2011), JDK 12 (2019), JDK 13 (2019)
 Tools
 appletviewer (for viewing Applets)
 javac (Java Compiler)
 java (Java Interpreter)
 jdb (Java Debugger)

Java as Portable
 Unlike other language compilers, Java complier
generates code (byte codes) for Universal Machine.
 Java Virtual Machine (JVM): Interprets bytecodes at
runtime

Java as Portable

Total Platform Independence
JAVA COMPILER
JAVA BYTE CODE
JAVA INTERPRETER
Windows 95 Macintosh Solaris Windows NT
(translator)
(same for all platforms)
(one for each different system)

Architecture Neutral & Portable
 Java Compiler - Java source code (file with
extension .java) to bytecode (file with extension
.class)
 Bytecode - an intermediate form, closer to
machine representation
 A interpreter (virtual machine) on any target
platform interprets the bytecode.

JAVA Program Structure

First JAVA Application
/* Hello World, first application, only output. */
import java.io.*;
public class Hello
{
public static void main (String [] args)
{
System.out.println(“Java Hello Worldn”);
} //end main
}//end class

How to get it running
 To compile:
 javac Hello.java
 To run:
 java Hello
 Note:
 Java is CASE SENSITIVE!!
 Whitespace is ignored by compiler
 File name has to be the same as class name in file.
 Need to import necessary class definitions

Java Path Setting
 On Error:
 Select Computer from the Start menu
 Choose System Properties from the context menu
 Click Advanced system settings > Advanced tab
 Click on Environment Variables, under System Variables, find PATH, and click on it.
 In the Edit windows, modify PATH by adding the location of the class to the value for
PATH.
 Reopen Command prompt window, and run your java code.

JAVA Keywords
abstract continue for new switch
assert default goto package synchronized
boolean do if private this
break double implements protected throw
byte else import public throws
case enum instanceof return transient
catch extends int short try
char final interface static void
class finally long strictfp volatile
const float native super while

Primitive Data Types
• Value of primitive type is not considered an object
• java.lang provides wrapper classes for each of
the primitive types
Dr. P. Victer Paul, Indian Institute of Information Technology Kottayam 1-32

Java Data Types
 Sizes fully specified by Java standard.
 Java is a very strongly typed language
 Integer types
 int (4 bytes signed)
 short (2 bytes signed)
 long (8 bytes signed) use suffix L (eg 1000000000L)
 byte (1 byte signed)
 Floating-point types
 float (4 bytes) use suffix F (eg 1.28F)
 double( 8 bytes)

Operators
Dr. P. Victer Paul, Indian Institute of Information Technology Kottayam 1-34

Flow Controls

End…

Java - OOPS and Java Basics

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Java - OOPS and Java Basics