rows = 2;
  columns = 3;
  n = rows*columns;
  labels = newArray(n);
  defaults = newArray(n);
  for (i=0; i<n; i++) {
    labels[i] = "Checkbox "+i+1;
    if ((i%2)==0)
       defaults[i] = true;
    else
       defaults[i] = false;
  }
  Dialog.create("Checkbox Group");
  Dialog.addCheckboxGroup(rows,columns,labels,defaults);
  Dialog.show();
  for (i=0; i<n; i++)
     print(labels[i]+": "+Dialog.getCheckbox());