5  Configuring DrJava and using the Command Prompt

5.1  Basic configuration requirement

Set the indentation level in DrJava to 4 spaces, by selecting Preferences -> Miscellaneous -> Indent Level -> 4. (Now you will be able to properly format your homework by using the indent key.)

5.2  Basic configuration suggestions

Display line numbers, by selecting Edit -> Preferences -> Display Options -> Show All Line Numbers.

Deactivate automatic updates, by selecting Edit -> Preferences -> Notifications -> Check for new versions -> none

Turn off “emacs style” backups (backup files with names that end in tilde), by unchecking Preferences -> Miscellaneous -> Keep emacs-style Backup Files.

5.3  Configuring DrJava to use Sedgewick and Wayne’s standard libraries

If you’re unsure, please wait until we do this in lab.

DrJava comes with many standard libraries built in. But in this course we also need the standard library provided by Sedgewick and Wayne, which adds a few convenient features to those libraries. We need this starting in section 1.5 of the textbook.

• First, download the file stdlib.jar which is a bundle containing all the libraries. Put it in the main directory where you are keeping things for this course.
• Second, configure DrJava to find the library, by selecting Edit -> Preferences -> Resource locations -> Extra classpath -> add -> now browse to where you put stdlib.jar

  Now click Apply and Ok to save the change.

• Finally, check that it is working: downloadTwentyQuestions.java and compile it. If that works, run the program from the interactions pane as usual.

Note: You can also download stdlib.jar from the booksite, specifically here.

Important note: Section 1.5 also discusses I/O redirection and piping, for which you will need to learn how to use the “shell” (also known as “terminal” or “command prompt”). We will cover this in lab at a later date.

5.4  Configuring your computer to use Java stand-alone at a Command Prompt

Important note: these are PRELIMINARY instructions, as an aid to walk through the process during lab. Please wait until lab unless you are quite confident about system administration for your computer.

5.4.1  Instructions for Windows 7

Add the Java compiler to your PATH variable:

• Select Start -> Control Panel -> search control panel, for “environment” -> Edit the system environment variables -> Environment Variables
• Under “System variables”, find the one named “Path”. Select Edit.
• Find the path to your Java installation (with help from TA). On some computers this path is “C:\Program Files\Java\jdk1.6.0_27\bin” but on others it is “C:\Program Files (x86)\Java\jdk1.6.0_26\bin”.
• Without deleting the existing path, prepend your Java installation path to the beginning, followed by a semicolon. So it should look like “C:\Program Files\Java\jdk1.6.0_27\bin;originalpath”
• Ok, Ok

Add StdLib to your CLASSPATH variable:

• Write down the path to where you saved stdlib.jar (which you already set in DrJava last week).
• Select Start -> Control Panel -> search control panel, for “environment” -> Edit the system environment variables -> Environment Variables
• Under “System variables”, look for one named “CLASSPATH”. If it exists, select Edit, otherwise select New.
• Without deleting the existing value, if it already existed, prepend the following to the beginning of the CLASSPATH variable:

       .;c:\Users\username\pathToTheFile\stdlib.jar;
  

  The period other punctuation marks should appear exactly. Use your own user name as well as the path to where you put stdlib.jar.
• Ok, Ok

Check that everything is working:

• Launch the command prompt by selecting Start -> All Programs -> Accessories -> Command Prompt
• At the prompt, type “java -version”. Get the TA to check that you see something like this:

  C:\Users\username>java -version
  java version "1.6.0_27"
  Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0_27-b07)
  Java HotSpot(TM) Client VM (build 1.6.0_27-b13, mixed mode, sharing)
  

  The version should be 1.6.something, possibly 0_26.
• Now at the prompt, type “javac -version”, and check that the result is something like this:

  C:\Users\username>javac -version
  javac 1.6.0_27
  

• Compile Average.java (in DrJava or at the command prompt), and then run it at the command prompt (not in DrJava!).

5.4.2  Instructions for Mac OS/X

Using DrJava or another text edit, edit the file /Users/username/.bashrc and add one line near the beginning of the file:

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

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

Close the Terminal and open a new one. See the Windows instructions for how to check that everything is working. If it does not work, in addition, try repeating the same instructions with the file /Users/username/.bash_profile

5.5  Using the Command Prompt

Preliminary instructions – we will explore this in lab.

5.5.1  For Windows 7:

Pin the Command Prompt to your start menu:

• Select Start -> All Programs -> Accessories
• right-click “Command Prompt” and choose “Pin to Start Menu”

Double-check that Java is set up properly:

Open a command prompt and enter “java -version”. You should see something like this.

C:\Users\username>java -version
java version "1.6.0_27"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0_27-b07)
Java HotSpot(TM) Client VM (build 1.6.0_27-b13, mixed mode, sharing)

Any version numbered like 1.6.any is ok.

Learn a few commands:

Here is a short tutorial on the Windows command prompt. It assumes that you have installed your course work in a directory named C:\introcs.

Note: We can now compile programs at the command prompt, but it is preferable to use DrJava. Pay attention to where you are saving and compiling, to avoid frustration about which copy of your program is running.

5.5.2  For Mac OS/X:

Open Applications -> Utilities -> Terminal

It works similarly to the command prompt in Windows but some commands have different names. Try reading the short tutorial on the Windows command prompt but when you try the commands yourself use these equivalents:

In OS/X, directory paths are written with forward/slash rather than backward\slash as in Windows.