TypedTableModel model = new TypedTableModel();
model.addColumn("f1", String.class);
model.addColumn("f2", String.class);
model.addColumn("f3", String.class);
model.addRow(null, null, null);
model.addRow("F1-0", null, null);
model.addRow("F1-1", "F2-1", null);
model.addRow(null, "F2-2", "F3-2");
model.addRow("F2-3", null, "F3-3");
return model;