// Sets the substance field to whatever substance is selected by the combo
 // box
 private void setSubstance() {
   String name = (String) substanceSelector.getSelectedItem();
   substance = (Substance) system.getEntity(name);
   if (metric != null) {
     metric.setSubstance(substance);
   }
   updateTarget();
 }
 public DoseObjectiveEditor(
     JFrame jf, ParameterSearchDoseResponseEditor e, TargetDoseObjective tdo) {
   this(jf, e);
   metric = tdo.getMetric();
   substance = metric.getSubstance();
   substanceSelector.setSelectedItem(substance.getName());
   objective = tdo.getObjective();
   weightField.setText((new Double(tdo.getWeight())).toString());
   updateTarget();
 }