Getting Ready for Java What is Java Java

Getting Ready for Java

What is Java? • Java is a programming language: a language that you can learn to write, and the computer can be made to understand • Java is currently a very popular language • Java is a large, powerful language – but it is not simple! • Compared to C++, Java is elegant

Declarations, statements, and comments • A declaration gives some information to the computer • A statement tells the computer to do something – Statements should really be called “commands” • Comments are ignored by the computer-they are explanations of your program for human beings to read

Syntax and semantics • Syntax is the “grammar” of the language – The syntax of Java is large, but finite – Syntax must be absolutely correct – The computer will point out every syntax error – Error messages may be helpful or misleading • Semantics is the “meaning” of your program – Semantic errors cause your answers to be wrong – You may or may not get error messages

Two aspects of Java • Java has syntax and semantics – This is where you begin – It is possible to learn everything about Java’s syntax and semantics – We will cover most of Java’s syntax and semantics • Java also has “packages” – Packages are sort of like vocabulary bundles – To be good at Java, you need to learn many packages – There are more Java packages than you can ever learn

Versions of Java • Java 1 – Java 1. 0: Original, not very good version – Java 1. 1: Greatly revised and improved • Java 2 – Java 1. 2: Includes “Swing” – Java 1. 3: Currently the best version – Java 1. 4 beta: The next version, still very buggy

Vocabulary I • JRE, Java Runtime Environment – The software that allows you to run Java programs on your computer • JDK, Java Development Kit; also • SDK, System Development Kit – The software that allows you to create and run Java programs on your computer • IDE, Interactive Development Environment – A tool that makes it easier to write programs

Vocabulary II • Beta software – Software that is new, untested, often buggy • Interface – the place where things touch each other – the way that distinct things communicate • GUI, Graphical User Interface – A way for the computer and the user to communicate via graphics (pictures) on the screen

Blue. J • Blue. J is an IDE (Interactive Development Environment). It includes – an editor, which you use to write your programs – a debugger, to help you find your mistakes – a viewer, to see the parts of your program – an easy way to run Java programs – an easy way to view documentation

Elegance • Powerful software can do everything you want to do--for example, Microsoft Word • Complex software is hard to learn and hard to use--for example, Microsoft Word • More power usually means more complexity • Elegant software somehow manages to be both powerful and simple • Blue. J is elegant

What You Need • 48 MB of RAM (64 MB recommended) • 166 MHz Pentium or better – Macintosh: must run Mac OS X • JDK 1. 3, preferably 1. 3. 1 • Blue. J 1. 1. 4 – does not work well with JDK 1. 4 beta • By the way: the JDK and Blue. J are free

Getting Ready • If you plan to use your own computer: – Download and install JDK 1. 3. 1 • http: //java. sun. com/j 2 se/1. 3/ – Download and install Blue. J 1. 1. 4 • http: //www. bluej. org/ – [Optional] Download the Java documentation • http: //java. sun. com/j 2 se/1. 3/docs. html

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