I know about IdentityHashMap
, but I need to use to something like "IdentitySet"
(use equals
as o1 == o2
). I'm going to use one to listen Observable list with "extractor" (JavaFX):
List<Person> deleteList = new ArrayList<>();
List<Person> addList = new ArrayList<>();
ObservableList<Person> list = FXCollections.observableArrayList(Person.extractor());
list.add(new Person("a",1));
list.add(new Person("b",2));
list.add(new Person("c",3));
list.addListener((ListChangeListener<Person>) observable -> {
if(observable.next()) {
if (observable.wasAdded()) {
addList.addAll(observable.getAddedSubList());
}
if (observable.wasUpdated()) {
deleteList.add(list.get(observable.getFrom()));
}
if (observable.wasRemoved()) {
deleteList.addAll(observable.getRemoved());
}
}
});
Person class:
public class Person {
private final StringProperty s;
private final DoubleProperty d;
//Getters and Setters
// ...
@Override
public int hashCode() {
int result = s != null ? s.getValue().hashCode() : 0;
result = 21 * result + (d != null ? Double.hashCode(d.getValue()) : 0);
return result;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Person person = (Person) o;
if (!s.getValue().equals(person.s.getValue())) return false;
return d.getValue().equals(person.d.getValue());
}
/**
*Extractor to observe changes in "Property" fields.
* @return extractor
*/
public static Callback<Person, Observable[]> extractor() {
return (Person p) -> new Observable[]{p.sProperty(), p.dProperty()};
}
I need to override equals
and hashCode
to solve my other issues.
Person p = new Person("a",1);
Set<Object> persons = new HashSet<>();
persons.add(p);
p.setD(999);
persons.add(p);
System.out.println(persons.size()); // size = 2;
persons.remove(p);
System.out.println(persons.size()); // size = 1;
thx, @BoristheSpider
Collections.newSetFromMap(...), returns a Set
backed by the specified map (in my case ➡️ IdentityHashMap
):
// get IdentytitySet wich wrap IdentityHashMap
Set<Person> persons = Collections.newSetFromMap(new IdentityHashMap<>())
// test
Person p = new Person("a",1);
Person p2 = new Person("a",1);
persons.add(p);
persons.add(p2);
System.out.println(persons.toString());
stdout (pretty print):
[
Person{
s=StringProperty [value: a],
d=DoubleProperty [value:1.0]
},
Person{
s=StringProperty [value: a],
d=DoubleProperty [value: 1.0]
}
]
p.setD(999);
persons.add(p);
System.out.println(persons.toString());
stdout (pretty print):
[
Person{
s=StringProperty [value: a],
d=DoubleProperty [value: 999.0]
},
Person{
s=StringProperty [value: a],
d=DoubleProperty [value: 1.0]
}
]
persons.remove(p)
System.out.println(persons.toString());
stdout (pretty print):
[
Person{
s=StringProperty [value: a],
d=DoubleProperty [value: 1.0]
}
]
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