Myujth

I have problems when sorting columns when there are empty cells.
I created a new Comparator for my codeMed column:

codeMed.setComparator(new Comparator<Integer>() 
 @Override
 public int compare(Integer o1, Integer o2) 

 if (o1 == null)return -1;
 if (o2 == null) return -1;
 return o1 < o2 ? -1 : o1 == o2 ? 0 :1;
 
 );

At first, it seems to work fine:

But if I decide to sort a different column then sort the codeMed column this happens:

I imagine the error is in the Comparator but I don't know what is the problem.

EDIT:
I want that the null values will always be at the bottom of the column.
I tried something like that:

if (codeMed.getSortType() == TableColumn.SortType.DESCENDING) 
 return (o1 != null ? o1 : Integer.MAX_VALUE) - (o2 != null ? o2 : Integer.MAX_VALUE);
 else if (codeMed.getSortType()==TableColumn.SortType.ASCENDING)
 return (o1 != null ? o1 : Integer.MIN_VALUE) - (o2 != null ? o2 : Integer.MIN_VALUE);

return 0;

But it doesn't work :/ (Maybe because of the problem that Slaw suggests)

My solution:

Thank you very much Jai, I adapt your code just because I want to use it for 2 different collumns:
Comparator<Integer> integerComparator = new Comparator<>()
@Override
public int compare(Integer o1, Integer o2)
final boolean isDesc = tabInfosPatient.getSortOrder().get(0).getSortType() == TableColumn.SortType.DESCENDING;
if (o1 == null && o2 == null) return 0;
else if (o1 == null) return isDesc ? -1 : 1;
else if (o2 == null) return isDesc ? 1 : -1;
else return Integer.compare(o1, o2);

;

I'm surprised it even worked once. This is what I think would work well:

codeMed.setComparator(new Comparator<Integer>() 
 @Override
 public int compare(Integer o1, Integer o2) 
 return (o1 != null ? o1 : Integer.MAX_VALUE) - (o2 != null ? o2 : Integer.MAX_VALUE);
 
 );

This would assume any null value is treated as if it represents the largest possible int value. This would force it to move to the bottom of the list in an ascending sorted column, or at the top if it is in a descending sorted column. If the reverse is desired, switch Integer.MAX_VALUE to Integer.MIN_VALUE.

What you did doesn't work because you have violated this:

The implementor must ensure that sgn(compare(x, y)) == -sgn(compare(y,
x)) for all x and y. (This implies that compare(x, y) must throw an
exception if and only if compare(y, x) throws an exception.)

An example of this violation is when o1 is 5 and o2 is null. In this case, compare(o1, o2) returns -1 and compare(o2, o1) returns -1 as well. One of them should return positive value while the other negative value, or both must return 0.

Update

This is what you need.

public class Model 
 private final ObjectProperty<Integer> v = new SimpleObjectProperty<>();

 public Model(Integer v) 
 this.v.setValue(v);
 

 public final ObjectProperty<Integer> vProperty() 
 return this.v;
 

 public final Integer getV() 
 return this.vProperty().get();
 

 public final void setV(final Integer v) 
 this.vProperty().set(v);
 


ObservableList<Model> list = FXCollections.observableArrayList();
list.addAll(new Model(20), new Model(-30), new Model(null), new Model(10));

TableView<Model> tv = new TableView<>();
TableColumn<Model, Integer> tc = new TableColumn<>();
tc.setCellValueFactory(new PropertyValueFactory<>("v"));
tv.getColumns().add(tc);
tv.setItems(list);

Comparator<Integer> ascComparator = (o1, o2) ->
 (o1 != null ? o1 : Integer.MAX_VALUE) - 
 (o2 != null ? o2 : Integer.MAX_VALUE);

Comparator<Integer> descComparator = (o1, o2) ->
 (o1 != null ? o1 : Integer.MIN_VALUE) - 
 (o2 != null ? o2 : Integer.MIN_VALUE);

@SuppressWarnings("unchecked")
Comparator<Integer> defaultComparator = TableColumn.DEFAULT_COMPARATOR;

tc.comparatorProperty().bind(
 Bindings.when(tc.sortTypeProperty().isEqualTo(SortType.ASCENDING))
 .then(ascComparator)
 .otherwise(
 Bindings.when(tc.sortTypeProperty().isEqualTo(SortType.DESCENDING))
 .then(descComparator)
 .otherwise(defaultComparator)));

Also, I would want to point out that while using Integer.MIN_VALUE and Integer.MAX_VALUE should work most of the time, there is a much higher risk of integer underflow and overflow problem, which I'm not sure if it's a problem for using comparators and comparables.

If you want to be more safe, then do a bunch of if-else:

Comparator<Integer> ascComparator = (o1, o2) -> 
 if (o1 == null && o2 == null) return 0;
 else if (o1 == null && o2 != null) return -1;
 else if (o1 != null && o2 == null) return 1;
 else return Integer.compare(o1, o2);
;

Update again

After looking at what you attempted, I realized that this works:

Comparator<Integer> comparator = (o1, o2) -> 
 final boolean isDesc = tc.getSortType() == SortType.DESCENDING;
 if (o1 == null && o2 == null) return 0;
 else if (o1 == null && o2 != null) return isDesc ? -1 : 1;
 else if (o1 != null && o2 == null) return isDesc ? 1 : -1;
 else return Integer.compare(o1, o2);
;