Getting column names from AbstractTableModel

Question

I cannot understand something using the constructor JTable(TableModel dm).

I use LinkedList to manage my data, so to display it, I expanded AbstractTableModel:

public class VolumeListTableModel extends AbstractTableModel {

    private static final long serialVersionUID = 1L;
    private LinkedList<Directory> datalist;
    private Object[] columnNames= {"ID", "Directory", "Wildcard"};


    public VolumeListTableModel(){
    }

    public void setDatalist(LinkedList<Directory> temp){
        this.datalist = temp;
    }

    public LinkedList<Directory> getDatalist(){
        return (LinkedList<Directory>) this.datalist.clone();
    }

    public Object[] getColumnNames() {
        return this.columnNames;    
    }

    @Override
    public int getColumnCount() {
        return Directory.numCols;
    }

    @Override
    public int getRowCount() {
        return this.datalist.size();
    }

    @Override
    public Object getValueAt(int row, int col) {

        Directory temp = this.datalist.get(row);

        switch(col){
        case 0:
            return temp.getId();
        case 1:
            return temp.getPath();
        case 2:
            return temp.getWildcard();
        default:
            return null;        
        }
    }

I am doing something wrong, because when I start my GUI, I get the column names marked as A, * B *, C.

Answer 1

There is no method called getColumnNames in AbstractTableModel, so I believe your method is ignored. The actual method you want to override is the getColumnName method.

VolumeListTableModel

public String getColumnName(int column) {
    return columnNames[column];
}

Answer 2

getColumnName,

return columnNames[column];

Answer 3

You must override this method:

public String getColumnName(int column)

Answer 4

AbstractTableModel does not have a getColumnNames method , but it is easy to implement:

public class VolumeListTableModel extends AbstractTableModel {

    // [...]

    public String[] getColumnNames() {

        String[] columnNames = new String[this.getColumnCount()];

        for (int i = 0, columnCount = this.getColumnCount(); i < columnCount; i++) {    
            columnNames[i] = this.getColumnName(i);
        }

        return columnNames;

    }

    // [...]

}