鉴于以下课程:
trait ModelWithId {
var id: Long = 0
}
case class EntityAttribute (
val entityId: UUID,
val attrName: String,
val stringVal: Option[String],
val boolVal: Option[Boolean],
val longVal: Option[Long],
val doubleVal: Option[Double],
val byteVal: Option[Array[Byte]]) extends ModelWithId{
override def toString() : String = {
"EntityAttribute(" + entityId.hashCode + "," + attrName.hashCode + "," +
stringVal.map{_.hashCode}.getOrElse(None) + "," + stringVal.hashCode+ "," +
boolVal.map{_.hashCode}.getOrElse(None) + "," + boolVal.hashCode+ "," +
longVal.map{_.hashCode}.getOrElse(None) + "," + longVal.hashCode+ "," +
doubleVal.map{_.hashCode}.getOrElse(None) + "," + doubleVal.hashCode+ "," +
byteVal.map{_.hashCode}.getOrElse(None) + ")"
}
}
以下比较功能:
val newAtttributes : List[EntityAttribute]
val withoutIds : List[EntityAttribute]
println("without: " + withoutIds)
println("new: " + newAtttributes)
val differences = newAtttributes.diff(withoutIds)
println("diff: " + differences)
if(newAtttributes.size == 1 && withoutIds.size == 1){
println("==: " + (newAtttributes.get(0) == withoutIds.get(0)))
println("equals: " + (newAtttributes.get(0).equals(withoutIds.get(0))))
println("hequals: " + (newAtttributes.get(0).hashCode == withoutIds.get(0).hashCode))
}
我得到的预期差异输出99次100次。偶尔,diff函数将返回一个空列表,它应该是一个列表。
示例:
without: List(EntityAttribute(428861607,-1147340381,None,120224,None,120224,56,-356863126,None,120224,None))
new: List(EntityAttribute(428861607,-1147340381,None,120224,None,120224,23,424930523,None,120224,None))
diff: List()
==: false
equals: false
hequals: false
通常在大约10-18次迭代后,我可以可靠地重现此错误。这两个列表来自不同的来源,因此它们的构造方式不同。我猜这与自动装箱或者糟糕的hashCode实现有关,但是我一直在抨击墙壁2天没有进展。
我正在使用scala 2.9.0-1。
答案 0 :(得分:-1)
这两个EntityAttribute
包含longVal
的不同值。案例类的默认equals
实现考虑了所有成员,因此使它们不相等。如果您只想使用成员的子集,则应定义自己的equals
和hashCode
。