MutableTable Regular Expression

Yes. If you wanted to match a | character without listing other possible characters in [] brackets, you'd need to escape it like \\| but it's ok while it's contained in [] brackets.

That should work, yes.

I'm a little confused though what this has to do with Mutable Tables...

Note also that your pattern is matching ^ as a character, not as a start-of-string placeholder; I'm not sure whether that's what you intended.

And actually, I wonder if the expression is a bit meaningless in the first place. The * after the characters in [] allows zero characters to be matched, which probably isn't what you want. Maybe you want:
    public static final String POINT_GROUP_REGEX = "[^|;&\\r\\n\\t]+";

Changing the * to + means the pattern requires at least one of the listed characters.

Changing the quantifier from * to +, as follows:

    public static final String POINT_GROUP_REGEX = "[^|;&\\r\\n\\t]+";

What I realy want is to prevent users from entering any of the three special characters  |;& in a mutable table used for "Group Names". As soon as a user enters any of those three special characters or any of the control characters, he should be prompted to change/correct his entry.

Here is the java routine that processes the Regular Expression:

        ColumnTableModel pointGroupsModel;
        Column groupID = getColumn(messages.getString("GroupIDTxt"), false, SystemwideConstants.POINT_GROUP_ID_ATTR, Integer.class, null,
                false, null);

        Column pointGroupName = getStringColumn(messages.getString("GroupNameTxt"), SystemwideConstants.POINT_GROUP_NAME_ATTR,
                new RegexEditor(SystemwideConstants.POINT_GROUP_REGEX, new InvalidStringHandler(messages.getString("GroupNameTxt"))));

        Column[] columns = new Column[]{groupID, pointGroupName};
        pointGroupsModel = new ColumnTableModel(columns, stemwideConstants.MAX_NUMBER_OF_POINT_GROUPS);

The problem is that after compiling and testing the code, the user can still enter those special characters.
Is the regular expression at fault ?

Paolo

Q: Is the regular expression at fault ?
A: Perhaps...

   Where, and how is the RegExp used?  Are we talking about a code in your setValueAt() method?