fundamentals of programming - · pdf file03-02-2015 · java •is a programming...

Fundamentals of Programming

By Budditha Hettige

Overview

• Exercises (Previous Lesson)

• The JAVA Programming Languages

• Java Virtual Machine

• Characteristics

• What is a class?

• JAVA Standards

• JAVA Keywords

• How Install JAVA

• Sample Java Program

2 Budditha Hettige ([email protected])

Exercises

Draw a flowchart for the following

1. Enter two number from key bard and print average

2. Enter three number and find the maximum number

3. Process of the ATM machine


JAVA

• Is a programming language created by James

Gosling from Sun Microsystems in 1991

• Is a general-purpose, class-based, object-

oriented Programming language

• is intended to let application developers

“write once, run anywhere.”

• Current version (JDK) 7u21

• URL : http://www.oracle.com/


Java cont…

• Java programming language consists – Java compiler:

Java compiler translates Java coding into

byte-code

– Java virtual machine(JVM)

Java virtual machine interprets this byte-code and runs the program

– Java class libraries

Java Class Library is a set of dynamically loadable libraries that Java applications can call at run time


Java Virtual Machine (JVM)

Architecture

JAVA Source File (.java)

JAVA Bite code (.class)

Java Compiler

Java Virtual Machine

Memory Manager

Byte code Verifier

Interpreter

Java API


JAVA Vs C++

7



Java Compiler

Java VM

C++ Source File (.cpp)

Executable program (.exe)

C++ Compiler

Operating system can

directly execute

JAVA VM can directly execute

Budditha Hettige ([email protected])

Characteristics

Java has the following properties

• Platform independent

• Object-orientated programming

language

• Strongly-typed programming language

• Interpreted and compiled language

• Automatic memory management


Platform independent

• Can Run on any Platform

– Windows

– Linux

– MaC OS

9



Java Compiler

Java VM


Object-orientated programming

language

• Object-oriented programming (OOP) is a programming paradigm that represents concepts as "objects" that have data fields (State) and methods (Behavior)

• What is an Objects? – Object is a software bundle of related state

and behavior

– Characteristics: state and behavior

– Example (Person) • State (Name, NIC, height)

• Behavior (Speech, Sleep, eat)

– Object is an instance of a class (instance is a specific realization of any object)


http://en.wikipedia.org/wiki/Object_(computer_science)

What is a class?

• A Java class is a group of Java

methods and variables

• Example (Person)

– State (Name, NIC, height)

– Behavior (Speech, Sleep, eat)

11

class Person

{

}


Requirements for Class name

• Class name must begin with letter of

the alphabet

• Contains only letters, digits,

underscores or dollar sign

• Cannot be a language reserved

keywords (public, class etc)

• Name cannot be following values (true,

false or null)


Java Class name standard

• Begin with uppercase letter

• No spaces

• Emphasizes new word with an initial uppercase letter

Example

• EmployeRecords

• Student

• FirstExample

• SampleProgram


Java Keywords


Install JAVA

• Download Java Development Kit (JDK)

– http://www.oracle.com

• RUN Installation setup

• SET PATH for the JAVA

• Test JAVA is working

• Video Link

– http://www.dscs.sjp.ac.lk/~budditha/java/vd/ins/install.html


http://www.oracle.com/

http://www.oracle.com/

Simple Java Program

• A class with a main Method public class FirstProgram { public static void main(String[] args) { System.out.println("Hello"); } }

16

Operating System

FirstProgram

Main Method Output


A class without a main Method public class FirstProgram { }

Operating System Can not Execute the program

17

Operating System

FirstProgram


Your first Java program

• Open a text editor (text pad, Notepad etc.)

• Type the following sample

• Save program as “FirstProgram.java”

public class FirstProgram

{

public static void main(String[] args)

{

System.out.println("Hello World");

}

}


Compile and RUN

• Using command prompt go to the place

where in your java file

• To Compile: type javac <space><fileName>

Javac FirstProgram.java

• To Run: type java<space><fileName>

Java FirstProgram

• Video Link

– http://www.dscs.sjp.ac.lk/~budditha/java/vd/s1/02.html


First Java program

20

public class FirstProgram

{

public static void main(String[] args)

{

System.out.println("Hello World");

}

}

Flow chart

Start

Display “Hello World”

End Budditha Hettige ([email protected])

Print Output on Command

window

• Function

– System.out.println(“Some Text”);

– System.out.print(“Some Text”);

• Example

public class FirstProgram { public static void main(String[] args) {

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


Escape Sequences

• A character preceded by a backslash (\) is an

escape sequence

• has special meaning to the compiler

Escape Sequence Description

\t Insert a tab in the text at this point.

\b Insert a backspace in the text at this point.

\n Insert a newline in the text at this point.

\r Insert a carriage return in the text at this point.

\f Insert a formfeed in the text at this point.

\' Insert a single quote character in the text at this point.

\" Insert a double quote character in the text at this point.

\\ Insert a backslash character in the text at this point.


ASCII art with JAVA • ASCII art is a graphic design technique that uses computers for

presentation and consists of pictures pieced together from the

95 printable (from a total of 128) characters defined by the

ASCII Standard from

23

System.out.println(" @ @ @ ");

System.out.println(" @ @ @ @ ");

System.out.println(" @ @ @ ");

System.out.println(" \\|/ ");

System.out.println(" | | | ");




System.out.println(" ( ) ");

System.out.println(" ^^^^^ "); Budditha Hettige ([email protected])

Exercise 1. Why JAVA is Platform independent?

2. What class ?

3. What is JAVA Runtime Environment (JRE) ?

4. What is JAVA Class file?

5. Write a JAVA Program to Display the Following

output

6. Try to run the above program on the Linux machine

24

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HSIT 2130

Fundamentals of Programming

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fundamentals of programming - · pdf file03-02-2015 · java •is a programming...

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