对不起......这个愚蠢/愚蠢的问题,伙计们:的HashMap与覆盖equals和hashCode不工作
为什么没有被应用equals()
和hashCode()
?
目前它们只能按照我对HashSet
的预期工作。
UPDATE
即使键值5重复,但是它不调用equals和hashCode。
我想将其应用于Value。
就像这个例子中HashSet调用equal和hashCode一样,为什么hashMap没有被调用equals和hashCode,即使是key。
UPDATE2 - ANSWER
HashMap中的键(类 - >的hashCode,等于)将被调用。 谢谢大家。 我对此有点困惑。 :)
public class Employee {
int id;
String name;
int phone;
public Employee(int id, String name, int phone) {
this.id = id;
this.name = name;
this.phone = phone;
}
// Getter Setter
@Override
public boolean equals(Object obj) {
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
final Employee other = (Employee) obj;
System.out.println("Employee - equals" + other.getPhone());
if (this.id != other.id) {
return false;
}
if ((this.name == null) ? (other.name != null) : !this.name.equals(other.name)) {
return false;
}
if (this.phone != other.phone) {
return false;
}
return true;
}
@Override
public int hashCode() {
System.out.println("Employee - hashCode");
int hash = 3;
hash = 67 * hash + this.id;
hash = 67 * hash + (this.name != null ? this.name.hashCode() : 0);
hash = 67 * hash + this.phone;
return hash;
}
}
____________________________________________________________________________________
public class MapClass {
public static void main(String[] args) {
Map<Integer,Employee> map = new HashMap<Integer,Employee>();
map.put(1, new Employee(1, "emp", 981));
map.put(2, new Employee(2, "emp2", 982));
map.put(3, new Employee(3, "emp3", 983));
map.put(4, new Employee(4, "emp4", 984));
map.put(5, new Employee(4, "emp4", 984));
**//UPDATE**
map.put(5, new Employee(4, "emp4", 984));
System.out.println("Finish Map" + map.size());
Set<Employee> set = new HashSet<Employee>();
set.add(new Employee(1, "emp", 981));
set.add(new Employee(2, "emp2", 982));
set.add(new Employee(2, "emp2", 982));
set.add(new Employee(3, "emp3", 983));
set.add(new Employee(4, "emp4", 984));
set.add(new Employee(4, "emp4", 984));
System.out.println(set.size());
}
}
输出为
Finish Map5
Employee - hashCode
Employee - hashCode
Employee - hashCode
Employee - equals982
Employee - equals982
Employee - hashCode
Employee - hashCode
Employee - hashCode
Employee - equals984
Employee - equals984
4
究竟是什么问题?请记住,在HashMap中,密钥被哈希,而不是值 –
我将如何调用哈希映射的hascode&equals –
Map调用equals和hashCode方法,并且这样做 - 对于整数键!如果您希望Map检查Employee hashCode和/或equals,那么Employee必须是Key而不是Value。 –