Customize JTable Column width

TableColumn col = tab1.getColumnModel().getColumn(0);
col.setPreferredWidth(50);
col = tab1.getColumnModel().getColumn(1);
col.setPreferredWidth(100);
col = tab1.getColumnModel().getColumn(2);
col.setPreferredWidth(300);

Set Tooltip in JTable Cell

JTable tab = new javax.swing.JTable(tabm3){
public Component prepareRenderer(TableCellRenderer renderer,
int rowIndex, int vColIndex) {
Component c = super.prepareRenderer(renderer, rowIndex, vColIndex);
if (c instanceof JComponent) {
JComponent jc = (JComponent)c;

jc.setToolTipText((String)getValueAt(rowIndex, vColIndex));


}
return c;
}
};

mysql datefomat query

select Date_format(column,'%d/%m/%y %r') from tablename

Max date of a month

calendar = new GregorianCalendar(yr,mon-1,dd);
int days = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);