ui/src/main/java/thredds/ui/datatype/prefs/DurationField.java
protected Object getEditValue() {
    String editValue = tf.getText().trim();
    if (editValue.length() == 0) return null; // empty ok

    try {
      return new TimeDuration( editValue);
    } catch (java.text.ParseException e) {
      return null;
    }
 }
protected Object getEditValue() {
    String editValue = tf.getText().trim();
    if (editValue.length() == 0) return null; // empty ok

    try {
      return new TimeDuration( editValue);
    } catch (java.text.ParseException e) {
      return null;
    }
 }
get current value from editComponent