Simple Pentaho TableModel

import java.util.Calendar;
import java.util.Date;
import org.pentaho.reporting.engine.classic.core.util.TypedTableModel;

//This creates the table model that will be passed to the report.
String[] columnNames = ["Date Value"];
Class[] columnTypes = [Date.class];
def myTable = new TypedTableModel(columnNames, columnTypes);

//This grabs the start date from the report
def startDate = dataRow.get("start_date");

//whenever you use dataRow, always follow it up with a check for null
if (startDate == null)
    //If null, return a blank table.
    return myTable;

//Create a calendar, it is easier to manipulate than the Date class.
def cal = Calendar.getInstance();
//Set the calendar to whatever is in our start date.
cal.setTime(startDate);

for(int i = 0; i < 5; i++) {
    //This adds seven days to the calendar
    cal.add(Calendar.DAY_OF_MONTH, 7);
    //This creates a new insertable object from our calendar
    Object [] insertValue = [cal.getTime()];
    //This inserts the insertable object into the table model.
    myTable.addRow(insertValue);
}

//send the table model back to the report.
return myTable;