Jaeki Song

Lecture 01Introduction to Java Programming

Instructor

• Name: Jaeki Song• Office: BA 712• Office Hours

Tuesday & Thursday 10:00-Noon or by appointment

• Office Phone: (806) 742-8036• E-mail: jsong@ba.ttu.edu• Website: http://jsong.ba.ttu.edu

Course Materials

• Required TextbookDeitel and Deitel, Java How to Program, 4th

Edition, Prentice Hall

Course Objectives

• Objectives– Introduce OOP using JAVA– Understand JAVA programming– Understand the issues related to web-

programming using JAVA– Emphasize critical thinking about new

developments

Grading

• First Exam: 20%

• Second Exam: 20%

• Third Exam: 30%

• Assignments: 30%

Course Structure

• Fundamentals of programming

• Object-oriented programming

• Graphics programming

• Developing comprehensive programming

Objectives

• Basics of Programming Language

• What is Java?

• Introduction to Java Applications

Program Development Life Cycle (PDLC)1. Analyze Problem- Review program specification- Meet with users- Identify program components

2. Design Program- Group activity into modules- Devise solution algorithms- Test solution algorithms

3. Code Program- Translate solution algorithm- Enter program code into computer4. Test Program

- Remove any syntax error- Remove any logic error

5. Formalize Solution- Review program code- Review documentation- Implement program

6. Maintain Program- Identify errors- Identify enhancements

Structured Programming

• Hierarchical Input Process Output (HIPO) chart

• Algorithmic Thinking– Pseudocode– Flowchart– Storyboard

Top-Down Design

• One method that is useful when defining the procedures to be used is termed Top-Down Design. With Top-Down Design you– break down a problem down into functional

tasks or parts;– break each part, or task, into sub-parts;– continue the ‘chunking-up’ process until the

sub-parts, or sub-tasks, are very simple and easily described.

HIPO Chart

Main

ProcessInitialization

DeclareVariable

Print Report

Read arecord

CalculateAccumulate

totalPrint

Detail Calculateaverage

Print totalAnd averages

Wrap-up

Calculatediscount

CalculateGross amount

Calculate netAmount due

Algorithmic Thinking

• Correct– Using logical constructs and valid data in an organized

way • The steps will be carried out correctly • The program will make suitable response

• Efficient– The program’s ability to deliver a results in a time short

enough to be useful and in a space small enough• An algorithm can be defined in various ways. Two

common ways include the use of pseudocode and flowchart

Pseudocode

• uses English-like phrases to describe the instructions– List the actions using

keywords

– Depicts logical grouping or structures using indentation

MAIN MODULE:Call InitializationCall ProcessCall Output

END

PROCESS MODULE:Do While not End of FileRead a recordCall CalculateCall AccumulatePrint Detail LineEnd Do

RETURN

CALCULATE MODULE:If Hours > 40 thenCall overtimeElseCall Regular timeEnd If

RETURN

Flow Chart

ProcessSymbol

Represent process

I/OSymbol

Makes data available for processing (input) orDisplaying (output) of process information

Decisionsymbol

Represents a decision that determines whichOf number of alternative paths is to be followed

Connectorsymbol

Represents any entry form, or exit to, another partof the flow chart

Terminalsymbol

Represents the beginning, the end, or a point of Interruption or delay in a program

Storyboard

Interest Calculator

Principal:

Interest Rate:

Months:

Amount Paid:

CalculateCalculate ClearClear

principalField

amtlField

clearButton

monthslField

calButton

monthsLabel

intLabel

principalLabel

intField

amtLabel

What is Java?

• Computer programming language– Computer program

• A set of instructions

– Programming language• A set of words, symbols, and codes

– Syntax• A set of grammar or rules that specify how the

instructions are to be written

History of Java

• Designed in the early of 1990s by Sun Microsystems

• Provide animation and interactivity on the World Wide Web– Web browsers have provided the opportunities

to run Java applets

• The fastest growing language

Java Language

• Standard language used for programming, creating applets, servlets, JavaBeans, and enterprise components

• Java is simple

• Java is object-oriented language

• Java is distributed

Java Language

• Java is interpreted– Need an interpreter to

run Java program

– The program are compiled into Java Virtual Machine (JVM) code called bytecode

Java Source Code

Java compiler

Java Bytecode Code

Java Interpreter

CPU

JVM

Java Language

• Java is robust– Reliabile

• Detect many problems

• Java is secure• Java is platform-independent• Java is portable

– Can be run on any platform without being recompiled

• Java is multithreaded

Java Virtual Machine (JVM)

• Interpreter for the Java programming language– a simple platform that all Java applications run

on.

• Comes with Java Development Kit (JDK)– Contains JVM and run-time system– Java 2 SDK

• www.sun.com

Java Environment• Editor

– Integrated Development Environment (IDE)• Jbuilder, J++, Forte, Visual Cafe

• Compiler– Translate into bytecode

• For Sun Microsystems- javac (included in SDK)• Class loader produces .class file

• Loading– Applications

• loaded and executed using Java Interpreter java example.class

– Applet• loaded in the browser and could be viewed by applet viewer using the html file in

which the applet is placed.

Creating First Application

• The Java 2 Platform, Standard Edition

• JBuilder4 or 5

JBuilder: Interface

Main menuProjecttoolbar

Projectpane

Structurepane

ContentpaneFile tab

File view tab

Example

/* Assignment 1 Printing on the screen Programmer: Jaeki Song Student ID : 999-99-9999 Date : September 2001 Program Name: Address */

public class Address{

public static void main(String[] args) //method header{ System.out.println(“ Jaeki Song”); System.out.println(“ 1234 89th Street”);

System.out.println(“ Lubbock, TX, 79413”); }

}

Documentation

• Comments– Block comment

/* ….. */

– Line comment: //– e.g.

/* Assignment 1 Printing on the screen Programmer: Jaeki Song Student ID : 999-99-9999

Date : September 2001 Program Name: Address */

Java Class

• Java program consists of pieces called classes– Existing classes in Java Class Libraries

• Known as Java APIs (Applications Programming Interfaces)

• Classes consists of pieces called methods– Perform tasks and return information

Java Class

• A single class resides in a single Java source file with extension .java

• public class Address { …. }• The source code is Address.java.

– The name of the class is the name of the file

• Class name and file name must match

Main Method

• The class which contains the main() method is the class that starts running the program

• Every Java application (not applet) has a main class

public class Address{ public static void main(String[] args) { … }}

Access Modifier

• Specifies the circumstances in which the class can be accessed– E.g.: public class Address

{

…….

}

• Public indicates that this code can be access by all objects and can be extended or used as a basis for another class

• The contents of the class must be enclosed in braces { }

Methods and Method Header

public static void main(String[] args) //method header{

……

}

The methodas accessible to all classes

This method is for class

Three parts• return value

• method name

• arguments lists

Void means that this methoddoes not return a value when it is called

Method name is main. Mainmethod is the usual starting point for all stand-alone Java program

Piece of data. args is an identifier for any string or character argument

Body Code

{ System.out.println(“ Jaeki Song”); System.out.println(“ 1234 89th Street”); System.out.println(“ Lubbock, TX, 79413”); }

Out is the object that represents the default display

System is the name of the class (program-defined class)

Println is the name of a method thattakes a string argument. It returns its value to theSystem.out device

Variable

• Used to store data– Variable declaration

• To use a variable, you declare it by telling the compiler the name of the variable as well as what type of data it represents

datatype variableNamee.gint x; //Declare x to be an integer variabledouble interest; char a; //Declare a to be a character

valueint x, y, z;

Assignment

• After a variable is declared, you can assign a value to it by using an assignment statementvariable = expression;

e.g.

x = 1; //Assing 1 to variable x

x = y + 1 ; //assign the addition of y and 1 to x

– You can declare variable and initialize it in one stepint x;

x = 1 int x = 1;

Constant

• A constant represents permanent data that never changesfinal datatype CONSTANTNAME = VALUE;

In java, the world final means that the constant cannot be changed.

e.g.final double PI = 3.14159;

Numeric Data Types

• The Java Built-In data type– int: always 32-bit signed integer.– short: 16-bit integer.– byte: 8-bit integer (new).– long: 64-bit singed integer.– float: 32-bit floating-point number.– double; 64-bit floating-point number.– char: Unicode (16-bit, language independent

character value, international standard.– boolean: true or false, false is not 0 in Java

Numeric Operators

Operator Example Equivalent

+= i+=8 i = i+8

-= f-=8.0 f = f-8.0

*= i*=8 i = i*8

/= i/=8 i = i/8

%= i%=8 i = i%8

Increment and Decrement Operators

• Increment or decrement a variable by 1X++ or X--; suffix

++X or –X; prefix• Suffix operator: the variable is used in the

expression first, then incremented or decremented by 1

• Prefix operator: the variable is first incremented or decremented by 1, then used in the expression

Relational Operators

• Relational operator

Operator Name Example Answer

< less than 1 < 2 true<= less than or equal to 1 <=2 true> greater than 1 > 2 false>= greater than or equal to 1 >= 2 false= = equal to 1 = = 2 false!= not equal to 1 != 2 true

Boolean Operators

• Boolean variable– A variable that holds a Boolean value (true or

false)

Operator Name Example

! Not&& and true && true true| | or false | | false false

Programming Style and Documentation

• Appropriate Comments– Every program has the following block comment

appear at the top of the source code file:/* Programmer: Jaeki Song

Course: ISQS 6337

File Name: Assign1XXXX.java

Description: A brief description of the program

*/

Programming Style and Documentation

• Naming conventions– Make sure the meanings of the descriptive means you choose are

straightforward– Names are case-sensitive

• For variables and methods– Use lowercase– If the name consists of several words, concatenate them into one, making the first

word lowercase and capitalizing the first letter of each subsequent worde.g: calculateSalary

• For class names– Capitalize the first letter of each word

e.g; ComputeSalary

• For constants– All letters are capitalized

e.g.: MAX_VALUE = 10

Programming Style and Documentation

• Proper indentation and spacing– Clear and easy to read

e.g.:

public class Test

{

public static void main(String args[])

{

System.out.println(“Example”);

}

}

Programming Errors

• Syntax error– Result from errors in cod construction

• E.g.: mistyping, omitting some necessary punctuation, using an opening brace without a corresponding closing brace

• Logical error– Occur when a program does not perform the way it was

intended to

• Run-time error– Cause a program to terminate abnormally

• E.g.– Input error: the user enters an unexpected input value that the program

cannot handle– Division by zero

Formatting Output

• Escape characters

Code Concept Result

\t Horizontal tab Moves insertion point eight spaces to the right

\b Backspace Moves insertion point one space to the left

\n New lineMoves insertion point down one line and to the leftmargin

\r Carriage return Moves insertion point to the left margin

\” Double quote Used to print a double quote character

Using Java Swing Class

• Refers to the new library of GUI– A component set that makes up all the objects of GUI

• Displays output using windows or dialog boxes– Input Dialog and Output Dialog

• Use packages– Predefined classes grouped into categories of related

classes called packages (sometimes called java class libraries or java applications programming interface (API))

– JOptionPane• Defined in a package called javax.swing

Output Dialog

• showMessageDialog ( null, “string”);– A method of class JOptionPane– Two arguments

• Syntax

JOptionPane.showMessageDialog(null, “string”);

Example: Output Dialogimport javax.swing.JOptionPane; //import class JOptionPane

public class Address{

public static void main(String[] args) //method header{ JOptionPane.showMessageDialog(

null, " Jaeki Song\n1234 89th Street\n Lubbock, TX, 79413"); System.exit(0); //terminate program }}

Output

Input Dialog

• Uses predefined dialog box from class JOptionPane called input dialog– Allows the user to input a value for use in the

program– Syntax

JOptionPane.showInputDialog(“ Enter first integer”);

Example: Add Integerimport javax.swing.JoptionPane;

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

String number1, number2; //first and second string entered by user int numInt1, numInt2, sum; number1 = JOptionPane.showInputDialog(“Enter first number”); number2 = JOptionPane.showInputDialog(“Enter second number”); numInt1 = Integer.parseInt(number1); numInt2 = Integer.parseInt(number2); sum = numInt1 + numInt2; JOptionPane.showMessageDialog(null, “The sum is “ + sum, “Results”,

JOptionPane.PLAIN_MESSAGE); System.exit(0); }}

Output

JDK Packages

Package Name Description

java.applet Classes to facilitate using applets

java.awtAbstract Window Toolkit; classes to Facilitate graphics user interfaces

java.netClasses used for networking and client/Server applications

java.io Classes to facilitate input and output

java.langClasses to facilitate data types, threads,Strings, and others

java.util Classes used for dates, vectors, and others