scala

# Nothing

#### trait Nothing extends Any

`Nothing` is - together with Null - at the bottom of Scala's type hierarchy.

`Nothing` is a subtype of every other type (including Null); there exist no instances of this type. Although type `Nothing` is uninhabited, it is nevertheless useful in several ways. For instance, the Scala library defines a value scala.collection.immutable.Nil of type `List[Nothing]`. Because lists are covariant in Scala, this makes scala.collection.immutable.Nil an instance of `List[T]`, for any element of type `T`.

Another usage for Nothing is the return type for methods which never return normally. One example is method error in sys, which always throws an exception.

Attributes
  final

Linear Supertypes
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### Abstract Value Members

1. #### def getClass (): java.lang.Class[_]

   Returns the runtime class representation of the object.

   Returns the runtime class representation of the object.

   returns

     a class object corresponding to the static type of the receiver

   Attributes
     abstract
   Definition Classes
     Any

### Concrete Value Members

1. #### def != (arg0: Any): Boolean

   Test two objects for inequality.

   Test two objects for inequality.

   returns

     `true` if !(this == that), false otherwise.

   Attributes
     final
   Definition Classes
     Any

2. #### def ## (): Int

   Equivalent to `x.hashCode` except for boxed numeric types.

   Equivalent to `x.hashCode` except for boxed numeric types. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them.

   returns

     a hash value consistent with ==

   Attributes
     final
   Definition Classes
     Any

3. #### def == (arg0: Any): Boolean

   Test two objects for equality.

   Test two objects for equality.

   returns

     `true` if the receiver object is equivalent to the argument; `false` otherwise.

   Attributes
     final
   Definition Classes
     Any

4. #### def asInstanceOf [T0] : T0

   Cast the receiver object to be of type `T0`.

   Cast the receiver object to be of type `T0`.

   Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression `1.asInstanceOf[String]` will throw a `ClassCastException` at runtime, while the expression `List(1).asInstanceOf[List[String]]` will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

   returns

     the receiver object.

   Attributes
     final
   Definition Classes
     Any

5. #### def equals (arg0: Any): Boolean

   Compares the receiver object (`this`) with the argument object (`that`) for equivalence.

   Compares the receiver object (`this`) with the argument object (`that`) for equivalence.

   The default implementations of this method is an equivalence relation:

   - It is reflexive: for any instance `x` of type `Any`, `x.equals(x)` should return `true`.
   - It is symmetric: for any instances `x` and `y` of type `Any`, `x.equals(y)` should return `true` if and only if `y.equals(x)` returns `true`.
   - It is transitive: for any instances `x`, `y`, and `z` of type `AnyRef` if `x.equals(y)` returns `true` and `y.equals(z)` returns `true`, then `x.equals(z)` should return `true`.

   If you override this method, you should verify that your implementation remains an equivalence relation. 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)`).

   returns

     `true` if the receiver object is equivalent to the argument; `false` otherwise.

   Definition Classes
     Any

6. #### def hashCode (): Int

   Calculate a hash code value for the object.

   Calculate a hash code value for the object.

   The default hashing algorithm is platform dependent.

   Note that it is allowed for two objects to have identical hash codes (`o1.hashCode.equals(o2.hashCode)`) yet not be equal (`o1.equals(o2)` returns `false`). A degenerate implementation could always return `0`. However, it is required that if two objects are equal (`o1.equals(o2)` returns `true`) that they have identical hash codes (`o1.hashCode.equals(o2.hashCode)`). Therefore, when overriding this method, be sure to verify that the behavior is consistent with the `equals` method.

   returns

     the hash code value for this object.

   Definition Classes
     Any

7. #### def isInstanceOf [T0] : Boolean

   Test whether the dynamic type of the receiver object is `T0`.

   Test whether the dynamic type of the receiver object is `T0`.

   Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression `1.isInstanceOf[String]` will return `false`, while the expression `List(1).isInstanceOf[List[String]]` will return `true`. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

   returns

     `true` if the receiver object is an instance of erasure of type `T0`; `false` otherwise.

   Attributes
     final
   Definition Classes
     Any

8. #### def toString (): String

   Returns a string representation of the object.

   Returns a string representation of the object.

   The default representation is platform dependent.

   returns

     a string representation of the object.

   Definition Classes
     Any

### Inherited from Any