JTable keeps sorting numbers as Strings

Question

I want to sort the table correctly comparing the correct classes, not strings. I'm using a TableRowSorter:

TableRowSorter sorter = new TableRowSorter<CustomModelTable>(modelData);
tablaEJ.setRowSorter(sorter);

I overrided the method getColumnClass in CustomModelTable so I get the correct class depending on the column's name (this was made because types are defined programatically):

@Override
    public Class getColumnClass(int columnIndex)
    {
        try {
            if (columnIndex < this.getColumnCount()) {
                String name = getColumnName(columnIndex); //This just gets the header of the column
                name = name.toLowerCase();
                switch (name) {
                    case "int":
                    case "int[]":
                    case "núm.":
                    case "int[][]": return Integer.class; //Or Class.forName("java.lang.Integer");
                    case "byte":
                    case "byte[]":
                    case "byte[][]": return Class.forName("java.lang.Byte");
                    case "long":
                    case "long[]":
                    case "long[][]": return Class.forName("java.lang.Long");
                    case "float":
                    case "float[]":
                    case "float[][]": return Class.forName("java.lang.Float");
                    case "double":
                    case "double[]":
                    case "double[][]": return Class.forName("java.lang.Double");
                    case "boolean":
                    case "boolean[]":
                    case "boolean[][]": return Class.forName("java.lang.Boolean");
                    case "char":
                    case "char[]":
                    case "char[][]": return Class.forName("java.lang.Character");
                    case "string":
                    case "string[]":
                    case "string[][]": return Class.forName("java.lang.String");
                    default: return Class.forName("java.lang.String");
                }
            }
        } catch (Exception e){

        }
        return null;
    }

Here's an screenshot: Table wrongly sorted

The most curious thing is that I print the types:

for (int i = 0; i < tablaEJ.getModel().getColumnCount(); i++) {
     System.out.println(tablaEJ.getModel().getColumnClass(i));
}

And it returns the expected output (print of the above table):

class java.lang.Integer
class java.lang.Integer
class java.lang.Integer
class java.lang.Integer

Honestly, I don't know what I'm doing wrong.

Answer 1

The "safe" way is to declare which column indices are numbers:

public static class CustomTableModel extends DefaultTableModel {
        private final List<Integer> columnIndicesWithNumbers = Arrays.asList(0);

        @Override
        public Class<?> getColumnClass(int columnIndex) {
            if (columnIndicesWithNumbers.contains(columnIndex))
                return Double.class;
            return super.getColumnClass(columnIndex);
        }
    }

Here is a complete example to test yourself:

public class SorterTest {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            DefaultTableModel dm = new CustomTableModel();
            dm.addColumn("Integers");
            dm.addColumn("Strings");
            //@formatter:off 
            Object[][] data = { 
                    { 1, "Something" }, { 102, "Something Else" }, 
                    { 55, "Something" }, { 66, "Something" },
                    { 1000, "Something" }, { 1524, "Something" }, 
                    { 5801, "Something" }, { -55, "Something" },};
            //@formatter:on
            for (Object[] row : data) {
                dm.addRow(row);
            }
            JTable table = new JTable(dm);
            table.setAutoCreateRowSorter(true);

            JOptionPane.showMessageDialog(null, new JScrollPane(table));
        });
    }

    public static class CustomTableModel extends DefaultTableModel {
        private final List<Integer> columnIndicesWithNumbers = Arrays.asList(0);

        @Override
        public Class<?> getColumnClass(int columnIndex) {
            if (columnIndicesWithNumbers.contains(columnIndex))
                return Double.class;
            return super.getColumnClass(columnIndex);
        }
    }
}

Preview:

After your clarifications in the comment section:

You can @Override getValueAt method in order to return integers instead of strings.

Full example:

public class SorterTest {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            DefaultTableModel dm = new CustomTableModel();
            dm.addColumn("Integers");
            dm.addColumn("Strings");
            //@formatter:off 
            Object[][] data = { 
                    { "1", "Something" }, { "102", "Something Else" }, 
                    { "55", "Something" }, { "66", "Something" },
                    { "1000", "Something" }, { "1524", "Something" }, 
                    { "5801", "Something" }, { "-55", "Something" },};
            //@formatter:on
            for (Object[] row : data) {
                dm.addRow(row);
            }
            JTable table = new JTable(dm);
            table.setAutoCreateRowSorter(true);

            JOptionPane.showMessageDialog(null, new JScrollPane(table));
        });
    }

    public static class CustomTableModel extends DefaultTableModel {
        private final List<Integer> columnIndicesWithNumbers = Arrays.asList(0);

        @Override
        public Object getValueAt(int row, int column) {
            Object value = super.getValueAt(row, column);
            if (columnIndicesWithNumbers.contains(column)) {
                return Double.parseDouble(String.valueOf(value));
            }
            return value;
        }

        @Override
        public Class<?> getColumnClass(int columnIndex) {
            if (columnIndicesWithNumbers.contains(columnIndex))
                return Double.class;
            return super.getColumnClass(columnIndex);
        }
    }
}

Answer 2

I think you shouldn't cast the types doing that. When defining the columns, you should instantiate the type of column before setting anything in.