Scala example source code file (Any.scala)

This example Scala source code file (Any.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

any, boolean, class, int, string, t0

The Any.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala

/** Class `Any` is the root of the Scala class hierarchy.  Every class in a Scala
 *  execution environment inherits directly or indirectly from this class.
 *
 * Starting with Scala 2.10 it is possible to directly extend `Any` using ''universal traits''.
 * A ''universal trait'' is a trait that extends `Any`, only has `def`s as members, and does no initialization.
 *
 * The main use case for universal traits is to allow basic inheritance of methods for [[scala.AnyVal value classes]].
 * For example,
 *
 * {{{
 *     trait Printable extends Any {
 *       def print(): Unit = println(this)
 *     }
 *     class Wrapper(val underlying: Int) extends AnyVal with Printable
 *
 *     val w = new Wrapper(3)
 *     w.print()
 * }}}
 *
 * See the [[http://docs.scala-lang.org/sips/pending/value-classes.html value classes guide]] for more
 * details on the interplay of universal traits and value classes.
 */
abstract class Any {
  /** Compares the receiver object (`this`) with the argument object (`that`) for equivalence.
   *
   *  Any implementation of this method should be an [[http://en.wikipedia.org/wiki/Equivalence_relation 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 [[scala.Int]].
   *  (`o1.hashCode.equals(o2.hashCode)`).
   *
   *  @param  that    the object to compare against this object for equality.
   *  @return         `true` if the receiver object is equivalent to the argument; `false` otherwise.
   */
  def equals(that: Any): Boolean

  /** 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.
   *
   *  @return   the hash code value for this object.
   */
  def hashCode(): Int

  /** Returns a string representation of the object.
   *
   *  The default representation is platform dependent.
   *
   *  @return a string representation of the object.
   */
  def toString(): String

  /** Returns the runtime class representation of the object.
   *
   *  @return a class object corresponding to the runtime type of the receiver.
   */
  def getClass(): Class[_]

  /** Test two objects for equality.
   *  The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.
   *
   *  @param  that  the object to compare against this object for equality.
   *  @return       `true` if the receiver object is equivalent to the argument; `false` otherwise.
   */
  final def ==(that: Any): Boolean = this equals that

  /** Test two objects for inequality.
   *
   *  @param  that  the object to compare against this object for equality.
   *  @return       `true` if !(this == that), false otherwise.
   */
  final def != (that: Any): Boolean = !(this == that)

  /** Equivalent to `x.hashCode` except for boxed numeric types and `null`.
   *  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.
   *  For `null` returns a hashcode where `null.hashCode` throws a
   *  `NullPointerException`.
   *
   *  @return   a hash value consistent with ==
   */
  final def ##(): Int = sys.error("##")

  /** 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.
   *
   *  @return `true` if the receiver object is an instance of erasure of type `T0`; `false` otherwise.
   */
  def isInstanceOf[T0]: Boolean = sys.error("isInstanceOf")

  /** 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.
   *
   *  @throws ClassCastException if the receiver object is not an instance of the erasure of type `T0`.
   *  @return the receiver object.
   */
  def asInstanceOf[T0]: T0 = sys.error("asInstanceOf")
}