IdentitySet / IdentityHashSet（使用IdentityHashMap）

Question

我知道IdentityHashMap，但是我需要使用“ identitySet ”之类的东西（它使用等于-> o1 == o2）。当我用“ extractor”（JavaFX）收听Observable列表时，我将使用一个：

 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());
            }
        }
    });

人类：

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()};
}

我需要重写equals / hashCode来解决其他问题。

    Person p = new Person("a",1);
    Set<Object> set = new HashSet<>();
    set.add(p);
    p.setD(9999);
    set.add(p);
    System.out.println(set.size());  // size = 2;

Answer 1

thx，@BoristheSpider => get Set，它包装了一个IdentityHashMap，使用Collections.newSetFromMap（）：

// get IdentytitySet wich wrap IdentityHashMap
Set<Person> set = Collections.newSetFromMap( new IdentityHashMap<>() ) 
//test 
Person p  = new Person("a",1);
Person p2 = new Person("a",1);
set.add(p);
set.add(p2);
p.setD(999999999);
set.add(p);//add Person with changed "d" to 999999999
System.out.println(set.toString());

打印：

[Person {s = StringProperty [值：a]，d = DoubleProperty [值：9.99999999E8]}，Person {s = StringProperty [值：a]，d = DoubleProperty [值：1.0]}]

Answer 2

您可以使用番石榴的Sets.newIdentityHashSet().

https://github.com/google/guava/wiki/CollectionUtilitiesExplained