Something like this:

    public static boolean equal(ItemSet set1, ItemSet set2,
            Constraints constraints) throws
CannotDetermineEqualityException {

        Set<TableColumn> constrainedTableColumns = constraints
                .getAllTableColumns();

        // Check if all table+columns in set1 have a constraint
        if (!constrainedTableColumns.containsAll(
                                   set1.getTableColumnSet())) {
            Set<TableColumn> unknownTableColumns
                                   = set1.getTableColumnSet();
            unknownTableColumns.removeAll(constrainedTableColumns);
            StringBuilder buf = new StringBuilder("No constraints for");
            for (TableColumn pair : unknownTableColumns) {
                buf.append(' ').append(pair);
            }
            throw new CannotDetermineEqualityException(buf.toString());
        }

        // Check if all table+columns in set2 have a constraint
        if (!constrainedTableColumns.containsAll(
                                   set2.getTableColumnSet())) {
            Set<TableColumn> unknownTableColumns
                                   = set2.getTableColumnSet();
            unknownTableColumns.removeAll(constrainedTableColumns);
            StringBuilder buf = new StringBuilder("No constraints for");
            for (TableColumn pair : unknownTableColumns) {
                buf.append(' ').append(pair);
            }
            throw new CannotDetermineEqualityException(buf.toString());
        }

        // Now we are interested in the included table-columns
        Set<TableColumn> includedTableColumns = constraints
                .getIncludedTableColumns();

        // For each included table+column, check if item in set1 equals
item in set2
        for (TableColumn tableColumn : includedTableColumns) {
            // Allowing more than 1 item for table+column in set
            // And if there are multiple items of the same
table+column, ...
            List<Item> items1 = set1.findAllItemsOf(tableColumn);
            List<Item> items2 = set2.findAllItemsOf(tableColumn);

            // ... then both sets must have the same number of items...
            if (items1.size() != items2.size()) {
                return false;
            }

            // ... and they must be equal in the same order
            Iterator<Item> i1 = items1.iterator();
            Iterator<Item> i2 = items2.iterator();
            for (; i1.hasNext() && i2.hasNext();) {
                Item item1 = i1.next();
                Item item2 = i2.next();
                if (!item1.equals(item2)) {
                    System.out.println(item1 + " not equal to " + item2);
                    return false;
                }
            }
        }
        return true;
    }