![19
A Simple Application
Example 1.1
//This application program prints Welcome
//to Java!
package chapter1;
public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!");
}
}
RunRunSourceSource
NOTE: To run the program,
install slide files on hard
disk.www.vibranttechnologies.co.in](https://image.slidesharecdn.com/java-course-in-mumbai-150915113849-lva1-app6892/85/Java-course-in-mumbai-19-320.jpg)
![30
Blocks
A pair of braces in a program
forms a block that groups
components of a program.
public class Test {
public static void main(String[] args) {
System.out.println("Welcome to Java!");
}
}
Class block
Method block
www.vibranttechnologies.co.in](https://image.slidesharecdn.com/java-course-in-mumbai-150915113849-lva1-app6892/85/Java-course-in-mumbai-30-320.jpg)
![33
main Method
The main method provides the
control of program flow. The
Java interpreter executes the
application by invoking the main
method.
The main method looks like this:
public static void main(String[]
args) { www.vibranttechnologies.co.in](https://image.slidesharecdn.com/java-course-in-mumbai-150915113849-lva1-app6892/85/Java-course-in-mumbai-33-320.jpg)
Java course-in-mumbai
- 1. Introduction to Java Programming Vibrant Technology & Computers Vashi,Navi Mumbai
- 4. 4 Introduction Java is a programming language and computing platform first released by Sun Microsystems in 1995. There are lots of applications and websites that will not work unless you have Java installed, and more are created every day. Java is fast, secure, and reliable. From laptops to datacenters, game consoles to scientific supercomputers, cell phones to the Internet, Java is everywhere! Java allows you to play online games, chat with people around the world, calculate your mortgage interest, and view images in 3D, just to name a few. It's also integral to the intranet applications and other e-business solutions that are the foundation of corporate computing. www.vibranttechnologies.co.in
- 5. 5 Course Objectives Upon completing the course, you will understand – Create, compile, and run Java programs – Primitive data types – Java control flow – Methods – Arrays (for teaching Java in two semesters, this could be the end) – Object-oriented programming – Core Java classes (Swing, exception, internationalization, multithreading, multimedia, I/O, networking, Java Collections Framework) www.vibranttechnologies.co.in
- 6. 6 Course Objectives, cont. You will be able to – Develop programs using Forte – Write simple programs using primitive data types, control statements, methods, and arrays. – Create and use methods – Develop a GUI interface and Java applets – Write interesting projects – Establish a firm foundation on Java concepts www.vibranttechnologies.co.in
- 7. 7 Book Chapters Part I: Fundamentals of Programming – Chapter 1 Introduction to Java – Chapter 2 Primitive Data Types and Operations – Chapter 3 Control Statements – Chapter 4 Methods – Chapter 5 Arrays www.vibranttechnologies.co.in
- 8. 8 Book Chapters, cont. Part II: Object-Oriented Programming – Chapter 6 Objects and Classes – Chapter 7 Strings – Chapter 8 Class Inheritance and Interfaces – Chapter 9 Object-Oriented Software Development www.vibranttechnologies.co.in
- 9. 9 Book Chapters, cont. Part III: GUI Programming – Chapter 10 Getting Started with GUI Programming – Chapter 11 Creating User Interfaces – Chapter 12 Applets and Advanced GUI www.vibranttechnologies.co.in
- 10. 10 Book Chapters, cont. Part IV: Developing Comprehensive Projects – Chapter 13 Exception Handling – Chapter 14 Internationalization – Chapter 15 Multithreading – Chapter 16 Multimedia – Chapter 17 Input and Output – Chapter 18 Networking – Chapter 19 Java Data Structures www.vibranttechnologies.co.in
- 11. 11 Chapter 1 Introduction to Java and Forte What Is Java? Getting Started With Java Programming – Create, Compile and Running a Java Application www.vibranttechnologies.co.in
- 12. 12 What Is Java? History Characteristics of Java www.vibranttechnologies.co.in
- 13. 13 History James Gosling and Sun Microsystems Oak Java, May 20, 1995, Sun World HotJava – The first Java-enabled Web browser JDK Evolutions J2SE, J2ME, and J2EE (not mentioned in the book, but could discuss here optionally) www.vibranttechnologies.co.in
- 14. 14 Characteristics of Java Java is simple Java is object-oriented Java is distributed Java is interpreted Java is robust Java is secure Java is architecture-neutral Java is portable Java’s performance Java is multithreaded Java is dynamic www.vibranttechnologies.co.in
- 15. 15 JDK Versions JDK 1.02 (1995) JDK 1.1 (1996) Java 2 SDK v 1.2 (a.k.a JDK 1.2, 1998) Java 2 SDK v 1.3 (a.k.a JDK 1.3, 2000) Java 2 SDK v 1.4 (a.k.a JDK 1.4, 2002) www.vibranttechnologies.co.in
- 16. 16 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. This book uses J2SE to introduce Java programming. www.vibranttechnologies.co.in
- 17. 17 Java IDE Tools Forte by Sun MicroSystems Borland JBuilder Microsoft Visual J++ WebGain Café IBM Visual Age for Java www.vibranttechnologies.co.in
- 18. 18 Getting Started with Java Programming A Simple Java Application Compiling Programs Executing Applications www.vibranttechnologies.co.in
- 19. 19 A Simple Application Example 1.1 //This application program prints Welcome //to Java! package chapter1; public class Welcome { public static void main(String[] args) { System.out.println("Welcome to Java!"); } } RunRunSourceSource NOTE: To run the program, install slide files on hard disk.www.vibranttechnologies.co.in
- 20. 20 Creating and Compiling Programs On command line – javac file.java Source 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 www.vibranttechnologies.co.in
- 21. 21 Executing Applications On command line – java classname Java Interpreter on Windows Java Interpreter on Sun Solaris Java Interpreter on Linux Bytecode ... www.vibranttechnologies.co.in
- 23. 23 Compiling and Running a Program Where are the files stored in the directory?c:example chapter1 Welcome.class Welcome.java chapter2 . . . Java source files and class files for Chapter 2 chapter19 Java source files and class files for Chapter 19 Welcome.java~ www.vibranttechnologies.co.in
- 24. 24 Anatomy of a Java Program Comments Package Reserved words Modifiers Statements Blocks Classes Methods The main method www.vibranttechnologies.co.in
- 25. 25 Comments In Java, comments are preceded by two slashes (//) in a line, or enclosed between /* and */ in one or multiple lines. When the compiler sees //, it ignores all text after // in the same line. When it sees /*, www.vibranttechnologies.co.in
- 26. 26 Package The second line in the program (package chapter1;) specifies a package name, chapter1, for the class Welcome. Forte compiles the source code in Welcome.java, generates Welcome.class, and stores Welcome.class in the chapter1 folder. www.vibranttechnologies.co.in
- 27. 27 Reserved Words Reserved words or keywords are words that have a specific meaning to the compiler and cannot be used for other purposes in the program. For example, when the compiler sees the word class, it understands that the word after class is the name for the class. Other reserved words in Example 1.1 www.vibranttechnologies.co.in
- 28. 28 Modifiers Java uses certain reserved words called modifiers that specify the properties of the data, methods, and classes and how they can be used. Examples of modifiers are public and static. Other modifiers are private, final, abstract, and protected. A public datum, method, or class can be accessed by other programs. A private datum or method cannot be accessed by other programs. Modifiers are discussed in Chapter 6, "Objects and Classes."www.vibranttechnologies.co.in
- 29. 29 Statements A statement represents an action or a sequence of actions. The statement System.out.println("Welcome to Java!") in the program in Example 1.1 is a statement to display the greeting "Welcome to Java!" Every statement in Java ends withwww.vibranttechnologies.co.in
- 30. 30 Blocks A pair of braces in a program forms a block that groups components of a program. public class Test { public static void main(String[] args) { System.out.println("Welcome to Java!"); } } Class block Method block www.vibranttechnologies.co.in
- 31. 31 Classes The class is the essential Java construct. A class is a template or blueprint for objects. To program in Java, you must understand classes and be able to write and use them. The mystery of the class will continue to be unveiled throughout this book. For now, though, understand that awww.vibranttechnologies.co.in
- 32. 32 Methods What is System.out.println? It is a method: a collection of statements that performs a sequence of operations to display a message on the console. It can be used even without fully understanding the details of how it works. It is used by invoking a statement with a string argument. The string argument is enclosed within parentheses. In this case, the argument is "Welcome to Java!" You can call the same println method with awww.vibranttechnologies.co.in
- 33. 33 main Method The main method provides the control of program flow. The Java interpreter executes the application by invoking the main method. The main method looks like this: public static void main(String[] args) { www.vibranttechnologies.co.in
- 34. 34 Displaying Text in a Message Dialog Box you can use the showMessageDialog method in the JOptionPane class. JOptionPane is one of the many predefined classes in the Java system, which can be reused rather than “reinventing the wheel.” RunRunSourceSource www.vibranttechnologies.co.in
- 35. 35 The showMessageDialog Method JOptionPane.showMessageDialog(null, "Welcome to Java!", "Example 1.2", JOptionPane.INFORMATION_MESSAGE)); www.vibranttechnologies.co.in
- 36. 36 The exit Method Use Exit to terminate the program and stop all threads. NOTE: When your program starts, a thread is spawned to run the program. When the showMessageDialog is invoked, a separate thread is spawned to run this method. The thread is not terminated even you close the dialog box. To terminate the thread, you have to invoke the exit method. www.vibranttechnologies.co.in
Editor's Notes
- #2: First Class: Introduction, Prerequisites, Advices, Syllabus Lab 1: Create a Java Project, Compile, and Run. Show syntax errors Print program Capture screen shots, and save it in Word, and print it. Homework One: Check in the class randomly.