Question

I’m making a graph-related program so I need to dynamically create/remove columns from a JTable to simulate the adjacency table. I already can create columns when desired but I cannot remove them, because if I remove a column and then I create another column the previous data (from the deleted column) is shown in the newest column.

I have read this is because the column data is not removed from the tablemodel. I have seen examples to hide or show columns but I need really to remove them so then when I get the 2-dimensional matrix of data I don’t have crossed references nor bad data.

First correction:

private DefaultTableModel removeCol(int id){
        DefaultTableModel tmp = new DefaultTableModel();
        int columnas = modelo.getColumnCount();
        for(int i=0;i<columnas;i++){
            if(i!=id)
                tmp.addColumn(modelo.getColumnName(i));
        }
        int rows = modelo.getRowCount();
        String datos[] = new String[columnas-1];
        for(int row=0;row<rows;row++){
            for(int col=0,sel=0;col<columnas;col++,sel++){
                if(col!=id)
                    datos[sel] = (String) modelo.getValueAt(row, col);
                else
                    sel--;
            }
            tmp.addRow(datos);
        }
        return tmp;

    }

When invoking:

   DefaultTableModel mo = removeCol(i);
    tblTrans = new JTable(mo);

Answer 1

An adjacency matrix may be more easily manipulated in an AbstractTableModel, where you can explicitly manipulate the rows to elide one column. In outline,

class MatrixModel extends AbstractTableModel {

    private int rows;
    private int cols;
    private Boolean[][] matrix;

    MatrixModel(int rows, int cols) {
        this.rows = rows;
        this.cols = cols;
        matrix = new Boolean[rows][cols];
    }

    public void deleteColumn(int col) {
        for (Boolean[] row : matrix) {
            Boolean[] newRow = new Boolean[row.length - 1];
            // TODO: copy remaining values
            row = newRow;
        }
        this.fireTableStructureChanged();
    }
    ...
}