// sort by filename
comparator = new Comparator<DataPoint>() {
public int compare(DataPoint inP1, DataPoint inP2) {
if (inP2 == null) return -1; // all nulls at end
if (inP1 == null) return 1;
// sort by filename
comparator = new Comparator<DataPoint>() {
public int compare(DataPoint inP1, DataPoint inP2) {
if (inP2 == null) return -1; // all nulls at end
if (inP1 == null) return 1;