29-Nov-15 Getting Ready for Java

2 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

3 Declarations, statements, 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

4 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

5 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

6 The programming cycle ACTIONS: THINGS: edit.java file compilerun (execute) input data (optional).class file ok results ok syntax errors runtime error logic errors ok

7 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: More new packages, no new syntax Java 1.4: Introduces the assert statement Java 5 Java 1.5: Available as beta; several additions to syntax

8 Vocabulary I JRE, Java Runtime Environment This is the software that allows you to run Java programs on your computer SDK, System Development Kit (previously called JDK, Java Development Kit) The software that allows you to create and run Java programs on your computer When you install the SDK, you get a JRE along with it IDE, Integrated Development Environment A tool that makes it easier to write programs

9 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

10 BlueJ BlueJ is an IDE (Integrated 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

11 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 BlueJ is elegant

12 What You Need 128 MB of RAM (256 MB recommended) 500 MHz Pentium or better Macintosh: must run Mac OS X Java JDK or 1.5 (includes JRE) BlueJ or 2.0 Earlier versions of BlueJ have serious problems If you have an older version, update! By the way: the SDK and BlueJ are free

13 Getting Ready If you plan to use your own computer: Download and install Java JDK (=SDK) Find where it says Download J2SE 5.0 RC and click DOWNLOAD in the JDK column If you have a Macintosh, get Java [Optional, but strongly recommended] Download the Java documentation from the same page Download and install BlueJ or newer

14 The End