Scala中a.ne(null)和!= null之间有什么区别？

Question

我一直在使用

a != null

检查这a不是一个空引用.但现在我遇到了另一种方式:

a.ne(null)

什么方式更好,它们有什么不同？

Answer 1

就像@Jack所说x ne null的那样等于!(x eq null).之间的差x != null和x ne null是!=检查值平等和ne供参考的相等性检查.

例:

scala> case class Foo(x: Int)
defined class Foo

scala> Foo(2) != Foo(2)
res0: Boolean = false

scala> Foo(2) ne Foo(2)
res1: Boolean = true

Answer 2

除了说@drexin和@Jack,ne在AnyRef中定义并且只存在参考类型.

scala> "null".ne(null)
res1: Boolean = true

scala> 1.ne(null)
<console>:5: error: type mismatch;
 found   : Int
 required: ?{val ne: ?}
Note that implicit conversions are not applicable because they are ambiguous:
 both method int2Integer in object Predef of type (Int)java.lang.Integer
 and method intWrapper in object Predef of type (Int)scala.runtime.RichInt
 are possible conversion functions from Int to ?{val ne: ?}
       1.ne(null)

scala> 1 != null
res2: Boolean = true