Setting the Classpath in Java

This page is obsolete.

To use our standard library files (StdDraw.java, StdIn.java, and StdOut.java), you can place them in the same directory as the main program you are writing. A drawback with this is approach is that you end up with many copies of the same library files, scattered in different directories. Java's classpath mechanism allows you to store and access the library files from a common directory.

Organizing the Shared Libraries

Place the shared library files (StdDraw.java, StdIn.java, and StdOut.java) in a commond directory, say C:\introcs. Go to that directory and compile them.

Setting the Classpath in DrJava

To set the classpath for DrJava:

• From DrJava, choose the menu option Edit -> Preferences -> Resource Locations -> Extra Classpath -> Add and select C:\introcs. Click the Apply button, then the OK button.

Setting the Classpath for the Windows Command Prompt

To set the classpath for the Windows XP Command Prompt:

• Select Start -> Control Panel -> System -> Advanced -> Environment Variables -> System Variables -> CLASSPATH.

• If the Classpath variable exists, prepend .;C:\introcs to the beginning of the CLASSPATH varible.

• If the CLASSPATH variable does not exist, select New. Type CLASSPATH for the variable name and .;C:\introcs for the variable value.

• Click OK three times.

Setting the Classpath in OS X

To set the classpath for the bash shell in OS X:

• Use your favorite text editor (e.g., TextEdit) to add the following line to the file /Users/username/.bashrc.

  export CLASSPATH=.:/Users/username/introcs/

  If the file doesn't exist, create a new one.

• Close the Terminal and open a new one. If it does not work, in addition, try repeating the same instructions with the file /Users/username/.profile or /Users/username/.bash_profile.

Troubleshooting

Here are a few suggestions that might help correct any installation woes you are experiencing. If you need assistance, don't hesitate to contact a staff member.

How can I check the value of my CLASSPATH variable?

• Windows Command Prompt Type the following at the command prompt.

  C:\introcs\hello\> echo %CLASSPATH%
  

  The CLASSPATH variable should begin with .;C:\introcs.
• OS X and Linux Type the following at the shell.

  echo $CLASSPATH