Github user suyanNone commented on the pull request:
https://github.com/apache/spark/pull/4055#issuecomment-71447811
@srowen, the original `hashCode()` generated by idea auto-generated
hashcode feature. Now I already refined by your comments.
About canEqual(), I just according <<programming in Scala>> describe:
```
to Resolve
warning: non variable type-argument T in type
pattern is unchecked since it is eliminated by erasure
case that: Branch[T] => this.elem == that.elem &&
```
```
class Branch[T](
val elem: T,
val left: Tree[T],
val right: Tree[T]
) extends Tree[T] {
override def equals(other: Any) = other match {
case that: Branch[_] => (that canEqual this) &&
this.elem == that.elem &&
this.left == that.left &&
this.right == that.right
case _ => false
}
def canEqual(other: Any) = other.isInstanceOf[Branch[_]]
override def hashCode: Int = 41 * (41 * (41 + elem.hashCode) +
left.hashCode) + right.hashCode
}
Listing 30.4 · A parameterized type with equals and
```
@cloud-fan , I think `31*hashcode + hashcode` is more common method to do
that.
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