Installing Java

If your computer uses Windows XP or 2000 or 98 and Java is not already installed on your computer, then you can download and install a copy for free. Go to http://java.sun.com/j2se On the right column of the web page, you will see links for downloading and installing Java. You may use either of J2SE 5.0 or J2SE 1.4.2. Further, when you go to the appropriate page, you may select either basic Java (``JDK'') or you may select Java plus the NetBeans IDE. (Java and NetBeans are large, so if you are tight on disk storage, maybe you don't want NetBeans.)

The download step is routine, and you should let the installation program install Java at the folder, say, C:\j2sdk1.4.2_04.

Once the installation finishes, you are ready to try Java.

Open a new command window, and type first, 

set path=C:\j2sdk1.4.2_04\bin
This resets the command window so that it knows that it should search the above folder to find the Java software. Next, type javac. You should see a long message like this: 
>javac
Usage: javac  
where possible options include:
  -g                        Generate all debugging info
  -g:none                   Generate no debugging info
  -g:{lines,vars,source}    Generate only some debugging info
  -nowarn                   Generate no warnings
  -verbose                  Output messages about what the compiler is doing
etc...
If you see instead, 
'javac' is not recognized as an internal or external command,
operable program or batch file.
Then recheck the folder where Java was installed on your computer and try again.

Now you are ready to use javac and java to compile and execute programs from the command window. Just remember --- each time you open a command window, type first, set path=C:\j2sdk1.4.2_04\bin

Permanently resetting the PATH variable

It is a bit annoying to type set path=C:\j2sdk1.4.2_04\bin every time you open a command window, and there is a clever repair --- you can reset permanently the value of Windows's PATH variable so that Windows knows once and for all that Java is available at C:\j2sdk1.4.2_04. Here is what you must do on Windows XP to reset the Path variable:

  1. press Start
  2. select Control Panel
  3. On the Control Panel window, in the left column, press Switch to classic view (If you don't see this text, go to the next step below.)
  4. Double click on the icon for System
  5. In the System window, click on Advanced
  6. Click on the button Environment Variables
  7. In the new window, scroll until you see the variable, Path; click on it
  8. Press Edit
  9. Carefully use the right arrow button to move to the end of the long sequence of folder names. At the very end, without including any extra blanks, type this: 
    ;C:\j2sdk1.4.2_04\bin
  10. Press OK twice.
These steps make Java known to Windows XP.

Now, check if you have done the job correctly: Open a new command window, type path, and you will see the text you edited for the Path variable. You should see ;C:\j2sdk1.4.2_04\bin at the end.

Next, type javac. You should see the message displayed earlier.