Jaeki Song Lecture 01 Introduction to Java Programming

Instructor Name: Jaeki Song Office: BA 712 Office Hours Tuesday & Thursday 10:00-Noon or by appointment Office Phone: (806) Website:

Course Materials Required Textbook Deitel and Deitel, Java How to Program, 4 th 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 B asics of Programming Language W hat is Java? I ntroduction 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 computer 4. 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 Process Initialization Declare Variable Print Report Read a record Calculate Accumulate total Print Detail Calculate average Print total And averages Wrap-up Calculate discount Calculate Gross amount Calculate net Amount 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 Initialization Call Process Call Output END PROCESS MODULE: Do While not End of File Read a record Call Calculate Call Accumulate Print Detail Line End Do RETURN CALCULATE MODULE: If Hours > 40 then Call overtime Else Call Regular time End If RETURN

Flow Chart Process Symbol Represent process I/O Symbol Makes data available for processing (input) or Displaying (output) of process information Decision symbol Represents a decision that determines which Of number of alternative paths is to be followed Connector symbol Represents any entry form, or exit to, another part of the flow chart Terminal symbol Represents the beginning, the end, or a point of Interruption or delay in a program

Storyboard Interest Calculator Principal: Interest Rate: Months: Amount Paid: Calculate Clear 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

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 menu Project toolbar Project pane Structure pane Content pane File tab File view tab

Example /* Assignment 1 Printing on the screen Programmer: Jaeki Song Student ID : 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(“ th 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 : 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 method as accessible to all classes This method is for class Three parts return value method name arguments lists Void means that this method does not return a value when it is called Method name is main. Main method 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(“ th 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 that takes a string argument. It returns its value to the System.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 variableName e.g int x; //Declare x to be an integer variable double interest; char a; //Declare a to be a character value int x, y, z;

Assignment After a variable is declared, you can assign a value to it by using an assignment statement variable = 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 step int x; x = 1 int x = 1;

Constant A constant represents permanent data that never changes final datatype CONSTANTNAME = VALUE; In java, the world final means that the constant cannot be changed. e.g. final double PI = ;

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 OperatorExampleEquivalent +=i+=8i = i+8 -=f-=8.0f = f-8.0 *=i*=8i = i*8 /=i/=8i = i/8 %=i%=8i = i%8

Increment and Decrement Operators Increment or decrement a variable by 1 X++ 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 && andtrue && true  true | |orfalse | | 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 word e.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 CodeConceptResult \t Horizontal tab Moves insertion point eight spaces to the right \b Backspace Moves insertion point one space to the left \n New line Moves insertion point down one line and to the left margin \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 Dialog import javax.swing.JOptionPane; //import class JOptionPane public class Address { public static void main(String[] args) //method header { JOptionPane.showMessageDialog( null, " Jaeki Song\n th 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 Integer import 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 NameDescription java.appletClasses to facilitate using applets java.awt Abstract Window Toolkit; classes to Facilitate graphics user interfaces java.net Classes used for networking and client/ Server applications java.ioClasses to facilitate input and output java.lang Classes to facilitate data types, threads, Strings, and others java.utilClasses used for dates, vectors, and others