oop - java - session 1

8/13/2019 OOP - Java - Session 1

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J2SE Core Java

Objective: To introduce the student to Core Java Prerequisites: Knowledge of objectoriented programming

Evaluation method:

Theory exam (objective/subjective/both) 40% weightage

Lab exam 40% weightage Assignments 20% weightage

List of Books / Other training material

Courseware:

The Complete Reference Java Eight Edition, Herbert Schidt/ TMH

Reference: Beginning Java 2 by Ivor Horton; Wrox Publication


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Session 1:

Learning Objectives

List and explain Java features

Differentiate between C++ and Java

Write a simple Java program HelloWorld


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Language Translators

Machine language is the only language capable of directly instructingthe CPU.

Every non machine language program instruction must be translatedinto machine language prior to execution.

Language Translators convert High-level code into Machinelanguage.

Interpreters translate one program statement at a time, as theprogram is running.

Compilers translate a complete program into machine language,then the machine language program is executed as needed.

Because compiled programs run faster than programs that aretranslated line by line by an interpreter, programmers usuallychoose compilers to translate frequently run business programs.


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Java History

Computer language innovation and development occurs for two

fundamental reasons:

1) To adapt to the changing environments and uses

2) To implement improvements in the art of programming

The development of Java was driven by both in equal measures.

Many Java features are inherited from the earlier languages:

C C++ Java


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Before Java: C

Designed by Dennis Ritchie in 1972.

Before C:

BASIC, COBOL, FORTRAN, PASCAL

C is structured, efficient, high-level language that could replace

assembly code when creating systems programs.


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Before Java: C++

Designed by Bjarne Stroustrup in 1979.

In response to the increased complexity of programs and respectiveimprovements in the programming paradigms and methods:

1) Assembler languages

2) High-level languages

3) Structured programming

4) Object-oriented programming (OOP)

OOP a methodology that helps organize complex programs through

the use of inheritance, encapsulation and polymorphism.

C++ extends C by adding object-oriented features.


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Java: History

In 1990, Sun Microsystems started a project called Green.

Objective: To develop software for consumer electronics.

Project was assigned to James Gosling, a veteran of classic networksoftware design. Others included Patrick Naughton, ChrisWarth, Ed

Frank, and Mike Sheridan.

The team started writing programs in C++ for embedding into

Set top boxes

Washing machines

VCRs

- Ovens

Aim was to make these appliances more intelligent.


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Java: History

C++ is powerful, but also dangerous.

The power and popularity of C derived from the extensive use ofpointers.

Incorrect use of pointers can cause memory leaks, leading the

program to crash.

Replacing pointers by references, and automating memorymanagement was the proposed solution.


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Java: History

Hence, the team built a new programming language called Oak,whichavoided potentially dangerous constructs in C++, such as

pointers, pointer arithmetic, operator overloading etc.

Introduced automatic memory management, freeing theprogrammer to concentrate on other things.

Architecture neutrality (Platform independence)

Many different CPUs are used as controllers in consumer electronicdevices (They may change as per the new trends in technology).

So, the software and programming language had to be architectureneutral.


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Java: History It was soon realized that these design goals of consumer electronics

perfectly suited an ideal programming language for the Internet andWWW, which should be:

Object-oriented (& support GUI) Robust Architecture neutral

Internet programming presented a BIG business opportunity. Muchbigger than programming for consumer electronics.

Java was re-targeted for the Internet

The team was expanded to include Bill Joy (developer of Unix), Arthurvan Hoff, Jonathan Payne, Frank Yellin, Tim Lindholm etc.

In 1994, an early web browser called WebRunner was written in Oak.WebRunner was later renamed HotJava.

In 1995, Oak was renamed Java.

A common story is that the name Java relates to the place from where

the developmentteam got its coffee. The name Java survived thetrade mark search.


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Programming language

Another programming language using which we can develop applets,standalone applications, web applications and enterprise applications.

Platform Independent

A Java program written and compiled on one machine can be executedon any other machine (irrespective of the operating

system/architecture)

Object Oriented

Complies to object oriented programming concepts. Your program isnot object oriented unless you code that way

Compiled and Interpreted

The .java file is compiled to a .class file and the .class file isinterpreted to machine code

What is Java?


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The Java Buzzwords

The key considerations were summed up by the Java

team in the following list of buzzwords:

Simple

Secure

Portable

Object-oriented Robust

Multithreaded

Architecture-neutral

Interpreted

High performance Distributed

Dynamic


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SimpleJava is designed to be easy for the professionalprogrammer to learn and use.

Object-oriented:A clean, usable, pragmatic approach to objects

Robust:Restricts the programmer to find the mistakes early,performs compile-time (strong typing) and run-time (exception-handling) checks, manages memory automatically.

Multithreaded:Supports multi-threaded programming for writingprogram that perform concurrent computations

Architecture-neutral and Portable:Java Virtual Machine provides a

platform independent environment for the execution of Java byte codeand can be ported to any machine.

The Java Buzzwords


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Interpreted and High-performance:Java programs are

compiled into an intermediate representation byte code:

a) Later interpreted by any JVM

b) Translated into the native machine code (JIT)

Distributed:Java handles TCP/IP protocols, accessing a resource

through its URL much like accessing a local file

Dynamic:Substantial amounts of run-time type information toverify and resolve access to objects at run-time.

Secure:Programs are confined to the Java execution environmentand cannot access other parts of the computer.

The Java Buzzwords


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The Java Platform

A platformis the hardware and software environment in which aprogram runs.

The Java platform differs from most other platforms in that it's asoftware-only platform that runs on top of other, hardware-based platforms.

The Java platform has two components:

The Java Virtual Machine (Java VM)

The Java Application Programming Interface (Java API)

The Java API is a large collection of ready-made software

components that provide many useful capabilities, such asgraphical user interface (GUI) widgets.

The Java API is grouped into libraries (packages) of relatedcomponents which allow you to do various things.


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Versions of Java

Java Language vs. Java Platform Current version of the languageis 1.7 (JDK 7)

Core language plus additional APIs is called the Java 2platform

Three versions of the Java 2 Platform, targeted at differentuses

Java 2 Standard Edition (J2SE)

The basic platform, which this module will cover Java 2 Enterprise Edition (J2EE)

For business applications, web services, mission-critical systems

Transaction processing, databases, distribution, replication

Java 2 Micro Edition (J2ME)

Very small Java environment for smart cards, mobile phones, andset-top boxes

Subset of the standard Java libraries aimed at limited size andprocessing power


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The Java SE PlatformDevelop and deploy Java applications on desktops and servers andembedded environments..


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The Java SE PlatformDevelop and deploy Java applications on desktops and servers andembedded environments..


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Introduction Java Virtual Machine

.class

file

Java Virtual Machine

.java file

Java

Compiler

UNIXMicrosoftMac


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Java Virtual Machine

Every Java interpreter, whether it's a Java development tool or a Webbrowser that can run Java applets, is an implementation of the Java

VM.The Java VM can also be implemented in hardware.

Java byte codes help make "write once, run anywhere" possible.

We can compile your Java program into byte codes on any platformthat has a Java compiler.

The byte codes can then be run on any implementation of the Java VM.


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Why Use Java?

Write less code: Comparisons of program metrics (class counts,

method counts, and so on) suggest that a program written in Java canbe four times smaller than the same program in C++.

Write better code: The Java language encourages good codingpractices, and its garbage collection helps you avoid memory leaks.

Develop programs faster: Your development time may be as muchas twice as fast versus writing the same program in C++.

Avoid platform dependencieswith 100% Pure Java

Write once, run anywhere: Because 100% Pure Java programs arecompiled into machine-independent byte codes, they run consistentlyon any Java platform.

Distribute software more easily: You can upgrade applets easilyfrom a central server. Applets take advantage of the Java feature ofallowing new classes to be loaded "on the fly," without recompiling theentire program.


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Java Programming Environment

Specification :

Java compiler: Transform Java programs into Java byte code

Java byte code: Intermediate representation for Java programs

Java interpreter: Read programs written in Java byte code andexecute them

Java virtual machine: Runtime system that provides variousservices to running programs

Java programming environment: Set of libraries that provideservices such as GUI, data structures, etc.

Java enabled browsers: Browsers that include a JVM + ability to

load programs from remote hosts


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Object Oriented Languages -A Comparison

Feature C++ Ada Java

Encapsulation Yes Yes YesInheritance Yes No Yes

Multiple Inherit. Yes No NoPolymorphism Yes Yes YesBinding (Early/Late) Both Early LateConcurrency Poor Difficult YesGarbage Collection No No Yes

Class Libraries Yes Limited Yes

C++: OOL ADA: OBL JAVA: Almost Pure OOL


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Java better than C++ ?

No Typedef, #Defines or Preprocessor

No Global Variables

No goto statements

No Pointers and pointer arithmetic

No Unsafe Structures

No Multiple Inheritance

No Operator Overloading

No Fragile Data Types


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Removed From C++

Operator overloading

Pointers and array of pointers

Multiple-Inheritance

typedef, #define

Copy constructors, Destructors

Templates

And other stuff....


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Added or Improved over C++

Interfaces: Type Vs. Class

Garbage collection

Exceptions (More powerful than C++)

Strings

Instance of

Packages

Multi-threading


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Types of Java Applications

Different ways to write/run a Java codes are:Application- A stand-alone program that can be invoked from

command line . A program that has amain()method

Applet- A program embedded in a web page , to be run whenthe page is browsed .

A program that contains nomainmethod

Application -Java interpreter

Applets- Java enabled web browser (Linked to HTML via tag in .html file)


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Java Program Structure

The Java programming language:

A program is made up of one or more classes

A class contains one or more methods

A method contains programstatements

A Java application always contains a method calledmain()


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// comments about the class

public class MyProgram

class header

class body

Comments can be added almost anywhere

{

}


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public class MyProgram

{

}

public static void main (String[] args)

{

}

// comments about the class

// comments about the method

method headermethod body


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Comments

Comments in a program are also called inline documentation They should be included to explain the purpose of the program and describe

processing steps

They do not affect how a program works

Java comments can take two forms:

// this comment runs to the end of the line

/* this comment runs to the terminatingsymbol, even across line breaks */

/** This kind of comment is a specialjavadocstyle comment */


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Java Program - Example


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A Simple Java Application

Define a class HelloWorld and store it into a file:HelloWorld.java:

public class HelloWorld {

public static void main (String[] args) {

System.out.println(Hello, World);}

}

Compile the program: javac HelloWorld.java

Execute the program: java HelloWorld

Output: Hello, World


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Compiling Programs

On command line

javac file.javaSource Code

Create/Modify Source Code

Compile Source Code

i.e. javac Welcome.java

Bytecode

Run Byteode

i.e. java Welcome

Result

If compilation errors

If runtime errors or incorrect result


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Executing Applications

On command line

java classname

Java

Interpreter

on Windows

Java

Interpreter

on Sun Solaris

Java

Interpreter

on Linux

Bytecode

...


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Next

basic programming constructs of Java

Classes and Objects in Java

new operator

Constructors

Overloading


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J2SE Core Java

PG-DAC

Aug-2013


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J2SE Core Java

Objective: To introduce the student to Core Java Prerequisites: Knowledge of objectoriented programming

Evaluation method:

Theory exam (objective/subjective/both) 40% weightage

Lab exam 40% weightage

Assignments 20% weightage

List of Books / Other training material

Courseware:

The Complete Reference Java Eight Edition, Herbert Schidt/ TMH

Reference: Beginning Java 2 by Ivor Horton; Wrox Publication

oop - java - session 1

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