CSC300: Eclipse Problems

(Click here for one slide per page)

If eclipse has lots of errors like these:

Then delete the file module-info.java.

Afterwards, select Project > Clean... > Clean All Projects > Clean

The most common problem with eclipse is that the compiler compliance level gets messed up. Try this. If it does not work, then contact me.

With the compliance level issue, you may get a lot of compiler errors, such as this:

To fix it, pull up eclipse preferences. On windows, this is under the window menu.

Navigate to the compiler pane so that you can see the compliance level.

If the compliance level is anything other than 17, set it to 17 and then save and follow the prompts to recompile your entire workspace. It will take a few seconds.

If the compliance level is already correct, then set it to 1.4, and then save and follow the prompts to recompile your entire workspace. Then repeat the process and set it back to 17.

This appears to be a bug in eclipse. Good news is that is it seems to happen at most once with students in this class.

If this did not fix your issue, contact me.

Suppose you had eclipse working and then one day, eclipse looks like this:

Try

  "Project" > "Clean..." > "Clean all projects"

If that does not work, try deleting potentially problematic files to re-create a fresh eclipse-workspace:

• Exit eclipse

• Using the finder or terminal, remove the following files/directories:

  • eclipse-workspace/.metadata
  • eclipse-workspace/algs4/.classpath
  • eclipse-workspace/algs4/.project

  If you are using finder on a mac, you may need to make these files visible. To do this, press "Command-Shift-. (period)"

• Restart eclipse. You should have a blank eclipse-workspace.

• Follow the previous instructions to show the algs4 project, by following the previous instructions to install the code from class, starting with File > New > Java Project

To show the package explorer, do this:

Once it is showing, you can adjust the view using the buttons:

You may see that the algs4 project is empty, like this:

You may get this Run As box in eclipse, like this:

Or this:

This means that the algs4 project is not initialized properly. Here are some steps:

• delete algs4 in eclipse follow the instructions again to re-create it

• If still not working, check that eclipse is running in the correct place. You can see where it is running by doing File > Switch Workspace. That will show you what directory/folder you are currently running in. Make sure that this is where you unzipped the material for the class. If not, switch, and try again.

The textbook code is written to run from the command line. We will not do this. Instead, we will edit the code in eclipse to provide the following, when necessary:

1. command line arguments
2. standard input
3. standard output

If the text runs the program:

  java Program arg1 arg2 < input.txt > /tmp/output.txt

We will add the following lines to the "main" method of our java program:

  public static void main(String[] args) {
    args = new String[] { "arg1", "agrg2" };
    StdIn.fromFile ("data/input.txt") 
    StdOut.toFile ("/tmp/output.txt")
    ...

Revised: 2023-09-12 22:12