Introduction To Java - MFC 158 G

Fall 2000

Week 1 Assignment - Learning development environments - August 29, 2000 and September 5, 2000

Due Tuesday (7pm) September 12

Objectives:

- To become familiar with the NT operating system and Solaris Unix operating system for use as a Java programming environment and runtime environment

- To become familiar with editing, compiling and running various types of Java programs.

- To set up your own web area on UBUNIX for displaying your Java applets.

- Nothing to hand in for this assignment.

Obtain all the source code for the lab

1. On your UBUNIX account, create a directory called week1_lab

2. Copy the lab files from ~fineberg/mfc158labs/week1 directory into your week1_lab directory

3. You're now ready to compile the programs

Compiling Java Programs (applications and applets)

Using Java version 1.2

You should run the latest version of Java (1.2). You can test which version you're running by entering:

> java -version

You should see something like:

java version "1.2.1"

Solaris VM (build Solaris_JDK_1.2.1_03, native threads, sunwjit)

Compiling your source code

To do this, issue the javac (java compile) commands for each of the source files (as shown below) :

Ø javac Hello.java

Ø javac HelloSwing.java

Ø javac Helloapplet.java

(You must supply the .java extension)

This will create java bytecode executables called Hello.class, Helloswing.class and Helloapplet.class

Executing your compiled code - a non-windowed Java application (character-based)

To execute a Java application, at the command line type:

> java Hello

You must NOT supply the file extension (which is actually .class)

You should see a simple "hellooooooo" statement

Executing your compiled code - a Windowed Java application (using the Swing library)

To execute a Java application, at the command line type:

> java HelloSwing (with the following conditions noted below)

- If running from a Windows (95/98/NT) machine (using the NT version of JDK) or a Sun workstation (using the Solaris version of JDK), a windows stating "hello Javaworld" will pop up.

- If running from a Windows (95/98/NT) machine and executing from a telnet window, you must have the product Exceed running, so that your workstation can emulate the behavior of a Sun workstation. This will allow the Xwindow to be displayed (containing the message "hello Javaworld"). We will review Exceed during the Lab.

You should see a pop-up window with a message "Hello Javaworld". Click OK to terminate it.

Executing your compiled code - an Applet

We execute applets by displaying HTML pages which reference the applets. We don't actually call applets up by themselves. The file Helloapplet.html has the necessary reference to the compiled program (Helloapplet.class).

Running applets locally - not using a web browser

To execute this Java applet, at the command line type:

> appletviewer Helloapplet.html (with the following conditions noted below)

- If running from a Windows (95/98/NT) machine (using the NT version of JDK) or a Sun workstation (using the Solaris version of JDK), a windows stating "hello Javaworld" will pop up.

- If running from a Windows (95/98/NT) machine and executing from a telnet window, you must have the product Exceed running, so that your workstation can emulate the behavior of a Sun workstation. This will allow the Xwindow to be displayed (containing the message "hello Javaworld"). We will review Exceed during the Lab.

You should see a page full of Hello world statements.

Publishing and running your Helloapplet applet on the internet

- If you haven't yet activated your own UB personal web page area, you can get the information off the references section of the course URL at: http://www.buffalo.edu/~fineberg/mfc158

- Copy the files: Helloapplet.html and Helloapplet.class over to your WWW root directory. This should be located on the UBUNIX cluster in the directory ~your_user_name/public_html

- Make sure the files have at least READ permission.

- Check by doing the command > ls -l

- You should see the permissions in the left margin

- R = read w = write x = execute

- To give the minimum security access, you can execute the CHMOD command by:

- > chmod 744 Helloapplet.html

- > chmod 744 Helloapplet.class

- You can now access the the applet using a browser, at the following URL:

www.buffalo.edu/~your_user_name/Helloapplet.html

Modifying code

- modify the wording of ("hello world", etc.) in your copy of the code to see the changes take effect (use javac to compile all types of applications)

- easy to use editors are: Xemacs or pico in Unix. Wordpad in Windows.

- You may need to stop and start your browser to see the changes take effect! Some browsers may have a cache set to not reload a page.

- Modify all three programs and rerun

Two important notes about names of files and classes in programs:

1. The source file name must be the same as the class name.

2. Case sensitivity is used even when compiling under Windows

95 or NT!!!!!