Compiling Your First Java Program

(Free Web Tutorials & Resources)

by Michael Thomas

Java First Steps Home Page

If you have trouble with any of the steps below see the table below called "Help Notes".

Steps
(Tested with JDK1.5.0)

Step 1:  Download files to compile

• Create a new directory to place the files you will work with.  You can do this using Windows Explorer or using DOS (click here for Help with DOS)

• The zip file you downloaded on the "Java First Steps Home Page" has a series of files that starts with "MyFirst_".  Move them to the directory you just created.

• Extract the files into the same directory.

• MyFirst_setpathjdk.bat - Edit this batch file to point to your "JDK bin" directory.  Each batch file will call it.  Step 4 & Step 5 will use this file.

• MyFirst_java_test.bat - Run this batch file (click on it in Win Explorer) to test that you can run: 
  java.exe, javac.exe, appletviewer.exe

• Do not proceed unless you can run the previous batch file without errors.

Step 2:  Compile your first Java Applet

• Compile and Run your first Java Applet.  Java Applets are designed to run in a browser. 

  • In Windows Explorer, click on "MyFirstApplet_compile.bat".  This will compile the .java source code and create a .class file.

  • In the DOS compile window, you will see the "javac" command.  Wait until you see the "pause" command.  There should be no errors.  Now press the "Enter" key.

  • Next click on "MyFirstApplet_view.bat".  This will load Sun's appletview and display just the applet that is located in the file "MyFirstApplet.htm".  In the appletviewer window you should see the words:  "Hello World from an Applet"

  • Next click on "MyFirstApplet.htm".  This will launch your default browser and should display the html file which will load the applet.

  • Next view the Browsers Java Console.  You will need to have access to the Java Console for debugging and development testing.

    • IE Steps:

      • If you are following the steps, IE should be browsing the Applet.  If not start IE.

      • Click on "View", then "Java Console".  If this option does not appear the you need to configure IE5.x (maybe others) with the following steps:

        • Goto: Tools, Internet Options, Advanced (tab). Next check the option "Java Console enabled" which is located in the "Microsoft VM" section.

Step 3:  Compile your first Java Application

• Compile and Run your first Java Application.  Java Applications are designed to on a local machine which has a JVM (Java Virtual Machine) loaded.  By the way, Java Servlets work the same way.

  • In windows Explorer, click on "MyFirstApplication_compile.bat".  This will compile the .java source code and create a .class file.

  • In the DOS compile window, you will see the "javac" command.  Wait until you see the "pause" command.  There should be no errors.  Now press the "Enter" key.

  • Next click on "MyFirstApplication_run.bat".  This bath file will call the command "java" and execute the .class file you created when you compiled the .java source.

  • You should see on the DOS console the words:  Hello World from an Application

Step 4: Configure your DOS Window

This info is very valuable if you need it.  Go ahead and do the following steps.  If you ever need more DOS buffer to store your compile errors and/or your DOS window does not have a scrollbar, then you will need this info.

• Launch a DOS window.  I've listed several ways.

  • Start, Programs, Accessories, Command Prompt (or DOS Prompt)

  • Start, Programs, DOS Prompt

  • Win NT:  Start, Run, cmd.exe

  • Win 95/98/NT:  Start, Run, command.com

• Additional note:  If you press ALT-ENTER while in the DOS window you will get a full DOS window.  ALT-ENTER again will minimize the window.  When you are finished with the DOS window type "exit" at the command line to close the DOS window.

• Next, right click on the title of the DOS command window and choose Properties.  Here is the following settings that I use vs Win NT 4.0 defaults:
  Note:  After making the changes, make sure you choose "Modify shortcut which started this window" or you changes will be lost.

  Option	New Settings	Original Settings
  Option Tab Command History * Buffer Size * # of Buffers Quick Edit Mode Insert Mode	201 4 empty empty	50 4 checked checked
  Layout Tab Screen Buffer Size Width Height Window Size Width Height	300 1900 80 25	80 25 80 25

Step 5:  Pat Your Self on the Back

Help Notes

 

Topic	Notes
Environment Variables: Path Classpath	DOS Environments: View the DOS Environment Variables. c:\> set | more -  This DOS command will show you all of the DOS environment variables and page break if neccessary. Changing the DOS Environment Variables. set CLASSPATH=.    - This sets the class path to the current directory.  Make sure you don't add extra spaces to this command! set CLASSPATH=     -  This will remove the CLASSPATH variable. DOS Variables: path & CLASSPATH path - shows the director order in which DOS will look for DOS Commands.  I like to have the JDK be the first in the list if your OS allows it.  (ex:  c:\jdk1.3\bin; c:\winnt; etc...) CLASSPATH - a variable that tells java which directories to look for classes.  You should have ".;" be the first in the list.  If you need to customize the CLASSPATH for a program use the -classpath compile option when compiling (ex: javac HelloWorld.java -classpath . ). General Notes - Environment Variables: User Variables Section Note:  Because some software programs create errors when installing, I always change the setttings for "temp" and "tmp". From: %USERPROFILE%\Local Settings\Temp To: c:\temp (make sure the directory exits) Win XP Start, Settings, Control Panel, System Click the tab "Advanced", then click "Environment Variables" WinNT (NT4.0 & NT2000) Start, Settings, Control Panel, System, Environment Next Click on the "System Variable" called "Path". Next modify the "value" field by putting the path at the end of the current value.  (Separate the paths with a ";"). Ex:  ....; c:\jdk1.3\bin Win 95/98 Steps Press Start, Run type:  msconfig Then hit the "Enter" key. Click on the Autoexec.bat tab Click on "set Path" line.  Then click "Edit" Right now you are viewing the Autoexec.bat file.  Be careful while you are in this file. See if you have a command that begins with "SET PATH =".  If you do, add the correct path as the first entry after the "SET PATH =".  Choose from the following: For JDK 1.2 add:  c:\jdk1.2\bin; For SDK 1.3 add:  c:\jdk1.3\bin; Note: If you don't have a "SET PATH" statement, add the following: set path = c:\jdk1.3\bin; Next, you must reboot. After you reboot go to a DOS prompt and type: path If  c:\jdk1.3\bin appears first your are completed.  If c:\windows and/or c:\windows\command is first, you maybe calling java.exe from those directories. Win ME Steps Press Start, Run type:  msconfig Then hit the "Enter" key. Click on the Environment tab Click on "Path" line.  Then click "Edit" Be careful and add the correct path.  Note - add the path as the first entry. For JDK 1.2 add:  c:\jdk1.2\bin; For SDK 1.3 add:  c:\jdk1.3\bin; Ex: c:\jdk1.3\bin; c:\windows; c:\windows\command; Click on "Apply" Now click on the "General" tab.  Make sure that the Normal option is selected.  If not you may get a message about "selective startup" after you reboot. Click on "OK" Next, you must reboot. After you reboot go to a DOS prompt and type: path If  c:\jdk1.3\bin appears first your are completed.  If c:\windows and/or c:\windows\command is first, you maybe calling java.exe from those directories.
CLASSPATH variable	CLASSPATH -
Goto a DOS prompt	Ways to get to a DOS prompt: First way:  Start, Programs, Command Prompt Second way: Start, Run, command.com
DOS Commands	Common DOS Commands Command Example Description Steps to Create a directory for this project. DOS Command.  Type a DOS prompt. c: md \class md \class\java md \class\java\j1 cd \class\java\j1 dir *.* This shows a list of the files in a directory. C: This takes you to the C: drive. cd class This changes your default directory to a subdirectory called class cd \class\java This changes your default directory to a directory called "java" which is in a folder called "class" which is in the root "\" directory of the C: drive. md \class Makes a directory called class under the root "\" directory. javac MyFirstApplication.java Compiles your program. java MyFirstApplication Runs a Java Application appletviewer MyFirstApplet.html Runs Sun's appletviewer that will display your applet in a window.  No html code is displayed.                www.easydos.com - Helpful info on DOS commands.
Dos Filenames	DOS (some OS versions) dir /x  - shows 8char short file names.  Some versions of DOS require short filenames when you CD or give pathnames.  This command is handy in those cases.  May not work for all OS's.
Errors	Common Errors & Solutions Error opening registry key 'Software\JavaSoft\Java Runtime Environment' when calling:  java <program name> Quick fix - give the full path for java:  ex: c:\jdk1.3\bin\java Reinstall the Java Runtime Environment (JRE)