Java Chapter 22 - Student

Why Java?

ADVANTAGESDISADVANTAGES Has _____________ capabilities__________ ( times) than languages compiled directly to machine code. Java requires the extra step of ____________ the bytecode before executing. Machine (platform) _______________ or “write once, run anywhere” Undergoing constant _____________ small language (easy to implement) but steadily growing into a robust language Still requires an ___________ for each machine to run the code supports __________ for executing multiple tasks at the same time Limited to abilities that all machines can produce since it has to run on all types of machines (e.g., lose the extra graphics abilities of SGIs) ___________ – applets prevented from malicious activity

Understanding O-O Object-oriented is defined as: Difference between OO languages and procedural languages: What are some objects you might create if you were asked to create: - Contact address application - Grade rolls for a course - Transcript details for students at a school - Search engine How are methods useful in objects? Once we create an object, how many times can we instantiate it? For example, could we create 4 Smiley objects from the examples used previously? How? How much code did we need to make this happen? Why was it easy? How does this relate to objects?

Security Applets cannot _____ or _____ files on the computer running the applet Applets cannot create ____________________ to other computers Applets cannot ________ a program on the computer that is running the applet Applets cannot read _______________ on the computer that is running the applet Windows that are displayed from an applet are displayed differently than windows from an application, so that the user knows where it came from What is the danger in allowing applets to read files? What is the danger in allowing applets to write files?

Modifying and Using Free Applets

Free applets available  Some provide source code and allow you to modify it as you like.  Be sure to read the copyright, licensing and agreements before you use Find an applet you want. MAKE SURE it includes the java SOURCE code, NOT just the.class files! 2. Download the files (if it's a.zip file, you'll need to extract the contents of the file) 3. Copy the.java file(s) into your IDE (e.g. Eclipse) or editor. 4. Compile and run the Java Applet.

Hosting your applet on the Web

Get your applet up and running on a host somewhere. First you need to get your applet ready without using an IDE such as Eclipse. Setting up the HTML file  Create a file (in your text editor).  Enter the following line, changing the XYZ to the name of your class.  This needs to be saved a file named exactly: "index.html" in lower case letters.  Modify the width and height to what you want.

Hosting your applet on the Web Hosting for free (or buy a domain – see below)  University accounts  Geocities ( Free (but they put ads up on your pages),   Another option: Buying a Domain Name (FYI, not necessary)  Register.com  Registar.com  Aplus.net  others... Uploading files  Upload the index.html, all the.class files, all the images and sound files necessary to make your applet work  Make sure your code referencing the image file names matches the actual file name (case sensitive!! This is important as Eclipse in Windows has been lazy, allowing any case)  NOTE: if your project read in from a local file (not a URL) or writes to a file, you need to remove that code before it will work on the Internet (see Security section).

Other Features through 3 rd Party Libraries

Other Features through 3rd-party libraries Some are free, some cost money Catch - users that view your website with your applet can usually only do so if they too have ______________________________________ or a run-time interpreter for these additional functionalities. Some of the available features include:  2D Graphics  3D Graphics  Virtual Reality  Video  Accessing Databases  MP3 playback  Music manipulation

Summary Why Java Object-Oriented Security Modifying and using free applets Hosting your applet on the Web Other features using 3 rd party libraries