CIS525 - Lecture#9 - October 4, 2000

CIS 525 10/4/00 Chap 6: Java is downloaded onto a local hardrive, where it runs its applications For this reason, yhou can run simple animation and games on the web Java: => derived from C++, syntax and declarations similar to C++ => class library/hierarchy, (similar to SmallTalk) => code is compiled into a language independent intermediate form => Sun maintains 'official' standard, still has lots of fragmentation,(Micorsoft J++, etc) myths about Java: * is only for web applications * is totally transparent across platforms * is simple, (I/O can be difficult to use) Tools for Java: 1) some text-based editor 2) Java compiler, (found in 'jdk') javac.exe is compiler .java, (use this extension when saving file from text editor) javac.exe will convert the text file, (.java), to a .class extension 3a) Java interpreter, (for stand-alone operation) javac.exe actually RUNS the application of .class OR 3b) Java enabled browser, or a utility called 'appletviewer.exe' 4) Java byte code verifier, (embedded in interpreter) Be sure to set path to avoid having to enter it in its entirety: example: path=C:\windows;C:\windows\command;c:\;c:\dos;c:\jdk1.1.4\bin See page 243 of Hall for a Hello World applet display in browser HelloWWW.html note: the dos command to view any source code is, for example c:\Java\Chapter6> type "_______" OR c:\Java\Chapter6> edit "_______"
Chapter 7 Object Oriented Programming in Java Instance Variable declaration, example; point P1 = new Point(2,11); scrollbar bar = new Scrollbar(); <= a constructor point P1 = window.location(); string String1 = new String("A String"); * This can be shortened to: string String2 = "Another String"; For ANY stand alone application, you must have; void main()(; Java conventions for naming: 1) use lower case for first letter of instance variable name, (firstName) 2) begin class names with uppercase 3) constants in all uppercase