trait Ordered[A] extends Comparable[A]
A trait for data that have a single, natural ordering. See scala.math.Ordering before using this trait for more information about whether to use scala.math.Ordering instead.
Classes that implement this trait can be sorted with scala.util.Sorting and can be compared with standard comparison operators (e.g. > and <).
Ordered should be used for data with a single, natural ordering (like integers) while Ordering allows for multiple ordering implementations. An Ordering instance will be implicitly created if necessary.
scala.math.Ordering is an alternative to this trait that allows multiple orderings to be defined for the same type.
scala.math.PartiallyOrdered is an alternative to this trait for partially ordered data.
For example, create a simple class that implements Ordered
and then sort it with scala.util.Sorting:
case class OrderedClass(n:Int) extends Ordered[OrderedClass] { def compare(that: OrderedClass) = this.n - that.n } val x = Array(OrderedClass(1), OrderedClass(5), OrderedClass(3)) scala.util.Sorting.quickSort(x) x
It is important that the equals
method for an instance of Ordered[A]
be consistent with the
compare method. However, due to limitations inherent in the type erasure semantics, there is no
reasonable way to provide a default implementation of equality for instances of Ordered[A]
.
Therefore, if you need to be able to use equality on an instance of Ordered[A]
you must
provide it yourself either when inheriting or instantiating.
It is important that the hashCode
method for an instance of Ordered[A]
be consistent with
the compare
method. However, it is not possible to provide a sensible default implementation.
Therefore, if you need to be able compute the hash of an instance of Ordered[A]
you must
provide it yourself either when inheriting or instantiating.
- Source
- Ordered.scala
- See also
- Alphabetic
- By Inheritance
- Ordered
- Comparable
- Any
- by any2stringadd
- by StringFormat
- by Ensuring
- by ArrowAssoc
- Hide All
- Show All
- Public
- Protected
Abstract Value Members
- abstract def compare(that: A): Int
Result of comparing
this
with operandthat
.Result of comparing
this
with operandthat
.Implement this method to determine how instances of A will be sorted.
Returns
x
where:x < 0
whenthis < that
x == 0
whenthis == that
x > 0
whenthis > that
- abstract def getClass(): Class[_ <: AnyRef]
Returns the runtime class representation of the object.
Returns the runtime class representation of the object.
- returns
a class object corresponding to the runtime type of the receiver.
- Definition Classes
- Any
Concrete Value Members
- final def !=(arg0: Any): Boolean
Test two objects for inequality.
Test two objects for inequality.
- returns
true
if !(this == that), false otherwise.
- Definition Classes
- Any
- final def ##(): Int
Equivalent to
x.hashCode
except for boxed numeric types andnull
.Equivalent to
x.hashCode
except for boxed numeric types andnull
. 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. Fornull
returns a hashcode wherenull.hashCode
throws aNullPointerException
.- returns
a hash value consistent with ==
- Definition Classes
- Any
- def +(other: String): String
- Implicit
- This member is added by an implicit conversion from Ordered[A] toany2stringadd[Ordered[A]] performed by method any2stringadd in scala.Predef.
- Definition Classes
- any2stringadd
- def ->[B](y: B): (Ordered[A], B)
- Implicit
- This member is added by an implicit conversion from Ordered[A] toArrowAssoc[Ordered[A]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @inline()
- def <(that: A): Boolean
Returns true if
this
is less thanthat
- def <=(that: A): Boolean
Returns true if
this
is less than or equal tothat
. - final def ==(arg0: Any): Boolean
Test two objects for equality.
Test two objects for equality. The expression
x == that
is equivalent toif (x eq null) that eq null else x.equals(that)
.- returns
true
if the receiver object is equivalent to the argument;false
otherwise.
- Definition Classes
- Any
- def >(that: A): Boolean
Returns true if
this
is greater thanthat
. - def >=(that: A): Boolean
Returns true if
this
is greater than or equal tothat
. - final 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 aClassCastException
at runtime, while the expressionList(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.
- Definition Classes
- Any
- Exceptions thrown
ClassCastException
if the receiver object is not an instance of the erasure of typeT0
.
- def compareTo(that: A): Int
Result of comparing
this
with operandthat
.Result of comparing
this
with operandthat
.- Definition Classes
- Ordered → Comparable
- def ensuring(cond: (Ordered[A]) => Boolean, msg: => Any): Ordered[A]
- Implicit
- This member is added by an implicit conversion from Ordered[A] toEnsuring[Ordered[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: (Ordered[A]) => Boolean): Ordered[A]
- Implicit
- This member is added by an implicit conversion from Ordered[A] toEnsuring[Ordered[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: Boolean, msg: => Any): Ordered[A]
- Implicit
- This member is added by an implicit conversion from Ordered[A] toEnsuring[Ordered[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: Boolean): Ordered[A]
- Implicit
- This member is added by an implicit conversion from Ordered[A] toEnsuring[Ordered[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- 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.Any implementation of this method should be an equivalence relation:
- It is reflexive: for any instance
x
of typeAny
,x.equals(x)
should returntrue
. - It is symmetric: for any instances
x
andy
of typeAny
,x.equals(y)
should returntrue
if and only ify.equals(x)
returnstrue
. - It is transitive: for any instances
x
,y
, andz
of typeAny
ifx.equals(y)
returnstrue
andy.equals(z)
returnstrue
, thenx.equals(z)
should returntrue
.
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)
returnstrue
) hash to the same scala.Int. (o1.hashCode.equals(o2.hashCode)
).- returns
true
if the receiver object is equivalent to the argument;false
otherwise.
- Definition Classes
- Any
- It is reflexive: for any instance
- def formatted(fmtstr: String): String
Returns string formatted according to given
format
string.Returns string formatted according to given
format
string. Format strings are as forString.format
(@see java.lang.String.format).- Implicit
- This member is added by an implicit conversion from Ordered[A] toStringFormat[Ordered[A]] performed by method StringFormat in scala.Predef.
- Definition Classes
- StringFormat
- Annotations
- @inline()
- 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)
returnsfalse
). A degenerate implementation could always return0
. However, it is required that if two objects are equal (o1.equals(o2)
returnstrue
) 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 theequals
method.- returns
the hash code value for this object.
- Definition Classes
- Any
- final 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 returnfalse
, while the expressionList(1).isInstanceOf[List[String]]
will returntrue
. 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 typeT0
;false
otherwise.
- Definition Classes
- Any
- 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
Deprecated Value Members
- def →[B](y: B): (Ordered[A], B)
- Implicit
- This member is added by an implicit conversion from Ordered[A] toArrowAssoc[Ordered[A]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @deprecated
- Deprecated
(Since version 2.13.0) Use
->
instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.
This is the documentation for the Scala standard library.
Package structure
The scala package contains core types like
Int
,Float
,Array
orOption
which are accessible in all Scala compilation units without explicit qualification or imports.Notable packages include:
scala.collection
and its sub-packages contain Scala's collections frameworkscala.collection.immutable
- Immutable, sequential data-structures such asVector
,List
,Range
,HashMap
orHashSet
scala.collection.mutable
- Mutable, sequential data-structures such asArrayBuffer
,StringBuilder
,HashMap
orHashSet
scala.collection.concurrent
- Mutable, concurrent data-structures such asTrieMap
scala.concurrent
- Primitives for concurrent programming such asFutures
andPromises
scala.io
- Input and output operationsscala.math
- Basic math functions and additional numeric types likeBigInt
andBigDecimal
scala.sys
- Interaction with other processes and the operating systemscala.util.matching
- Regular expressionsOther packages exist. See the complete list on the right.
Additional parts of the standard library are shipped as separate libraries. These include:
scala.reflect
- Scala's reflection API (scala-reflect.jar)scala.xml
- XML parsing, manipulation, and serialization (scala-xml.jar)scala.collection.parallel
- Parallel collections (scala-parallel-collections.jar)scala.util.parsing
- Parser combinators (scala-parser-combinators.jar)scala.swing
- A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)Automatic imports
Identifiers in the scala package and the
scala.Predef
object are always in scope by default.Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example,
List
is an alias forscala.collection.immutable.List
.Other aliases refer to classes provided by the underlying platform. For example, on the JVM,
String
is an alias forjava.lang.String
.