对不起,关于这个愚蠢的问题,大家:
为什么equals()
和hashCode()
没有被应用?
目前它们只在HashSet
中按照我的预期运行。
更新
即使键值5重复了,它也没有调用equals
和hashCode
。
我想在值上也应用它。
就像在这个例子中HashSet
调用equal和hashCode一样,为什么HashMap
甚至在键上也不调用equals和hashCode呢?
更新2-答案
HashMap
的键(类 ->HashCode,equals)会被调用。
谢谢所有人。
我有点困惑。
:)
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());
}
}
输出结果为
Finish Map5
Employee - hashCode
Employee - hashCode
Employee - hashCode
Employee - equals982
Employee - equals982
Employee - hashCode
Employee - hashCode
Employee - hashCode
Employee - equals984
Employee - equals984
4