Question

我有两组喷气机,我想接上两组的交叉点。这套装置中的物体就是这样。

@BeanInfo
class User {

  @JsonProperty
  @BeanProperty
  var name:String = ""

  @JsonProperty
  @BeanProperty
  var id:Long = 0

  override def toString = name

  override def equals(other: Any)= other match {
      case other:User => other.id == this.id
      case _ => false
   }

}

In another class I get the sets of users and want to see the intersection.

val myFriends = friendService.getFriends("me")
val friendsFriends = friendService.getFriends("otheruser")
println(myFriends & friendsFriends)

以上代码不使用和印刷

Set()

然而,如果我用 for子手工操作套件,则我获得预期结果。

var matchedFriends:scala.collection.mutable.Set[User] = new HashSet[User]()    
myFriends.foreach(myFriend => {
  friendsFriends.foreach(myFriend => {
      if(myFriend == myFriend){
        matchedFriends.add(myFriend)
      }
  })
})
println(matchedFriends)

以上编码印刷

Set(Matt, Cass, Joe, Erin)

这部法律是公正的。

val set1 = Set(1, 2, 3, 4)
val set2 = Set(4,5,6,7,1)

println(set1 & set2)

以上印刷

Set(1, 4)

Do the set operations & &- etc.. only work on primitive objects ? Do I have to do something additional to my user object for this to work ?

Answer 1

我对这一点不持100%的肯定态度,但我认为,你的问题在于没有相应的习俗()实施“条码”。我感到惊讶的是,你的洗衣机完全在发挥作用,实际上......

当然,由于你没有打上<代码>hashCode,你通过每套作品的成分进行手工操作:

Answer 2

From JavaDoc:

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

From Scala Doc:

Additionally, when overriding this method it is usually necessary to override hashCode to ensure that objects which are "equal" (o1.equals(o2) returns true) hash to the same Int. (o1.hashCode.equals(o2.hashCode)).

<代码>Set不适用,因为您打破了<代码>hashCode/code>。页: 1

Answer 3

当优先于<代码>等于时,总是优先于<代码>hashCode/code>。

友情链接