HashMap使用override equals和hashCode不起作用

Question

对不起......关于这个愚蠢/愚蠢的问题,伙计们:

为什么不equals()和hashCode()被应用？

目前他们只是按照我的预期工作HashSet.

UPDATE

EVEN键值5重复但不调用equals和hashCode.

我也想在Value上应用它.

就像在这个例子中HashSet调用equal和hashCode一样,为什么hashMap不被称为equals和hashCode,即使对于key也是如此.

更新2 - 答案

将调用HashMap的键(class-> HashCode,equals).谢谢你们.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());
    }
}

输出是

Finish Map5
Employee -  hashCode
Employee -  hashCode
Employee -  hashCode
Employee -  equals982
Employee -  equals982
Employee -  hashCode
Employee -  hashCode
Employee -  hashCode
Employee -  equals984
Employee -  equals984
4

Answer 1

EVEN键值5重复但不调用equals和hashCode

是的,它会在键上调用hashCode,即Integer.

我也想在Value上应用它

现实的剂量:Java HashMaps不会那样工作.他们只检查重复项的密钥,而不是值,这是应该的.

如果您希望在Map中检查Employee的哈希,那么它必须是密钥.期.

另一种可能的解决方案是下载其中一个可用的多图.

编辑 以查看它正在调用hashCode和equals,将Map的键类型更改为如下所示:

class MyInt {
   private Integer i;

   public MyInt(Integer i) {
      this.i = i;
   }

   public Integer getI() {
      return i;
   }

   @Override
   public int hashCode() {
      System.out.println("MyInt HashCode: " + i.hashCode());
     return i.hashCode();
   }

   @Override
   public boolean equals(Object obj) {
      System.out.printf("MyInt equals: [%s, %s]%n", i, obj);
      if (this == obj)
         return true;
      if (obj == null)
         return false;
      if (getClass() != obj.getClass())
         return false;
      MyInt other = (MyInt) obj;
      if (i == null) {
         if (other.i != null)
            return false;
      } else if (!i.equals(other.i))
         return false;
      return true;
   }

   @Override
   public String toString() {
      return i.toString();
   }

}

然后像这样填充你的地图:

   Map<MyInt,Employee> map = new HashMap<MyInt,Employee>();
   map.put(new MyInt(1), new Employee(1, "emp", 981));
   map.put(new MyInt(2), new Employee(2, "emp2", 982));
   map.put(new MyInt(3), new Employee(3, "emp3", 983));
   map.put(new MyInt(4), new Employee(4, "emp4", 984));
   map.put(new MyInt(5), new Employee(4, "emp4", 984));
   map.put(new MyInt(5), new Employee(4, "emp4", 984));

你会看到:

MyInt HashCode: 1
MyInt HashCode: 2
MyInt HashCode: 3
MyInt HashCode: 4
MyInt HashCode: 5
MyInt HashCode: 5
MyInt equals: [5, 5]