Hi Holly,
If you need to show data in columns,
you should consider using a JTable, which is a spreadsheet-like thing. That's certainly what I would do.
If you have to use JTextArea -- because a school assignment says so, for example -- then your main alternative is just to use TAB ("\t", or ASCII 9) characters to separate the columns -- although unless every datum is the same size, even that's no guarantee everything will line up.