We need a whole WithFilter class to honor the "doesn't create a new collection" contract even though it seems unlikely to matter much in a collection with max size 1.
A method that should be called from every well-designed equals method that is open to be overridden in a subclass.
A method that should be called from every well-designed equals method that is open to be overridden in a subclass. See Programming in Scala, Chapter 28 for discussion and design.
the value being probed for possible equality
true if this instance can possibly equal that, otherwise false
Returns the option's value.
Returns the option's value.
Returns true if the option is None, false otherwise.
Returns true if the option is None, false otherwise.
The size of this product.
The size of this product.
for a product A(x_1, ..., x_k), returns k
The nth element of this product, 0-based.
The nth element of this product, 0-based. In other words, for a
product A(x_1, ..., x_k), returns x_(n+1) where 0 < n < k.
the index of the element to return
the element n elements after the first element
Test two objects for inequality.
Test two objects for inequality.
true if !(this == that), false otherwise.
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.
a hash value consistent with ==
Test two objects for equality.
Test two objects for equality.
true if the receiver object is equivalent to the argument; false otherwise.
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.
the receiver object.
Create a copy of the receiver object.
Returns a Some containing the result of
applying pf to this Option's contained
value, if this option is
nonempty and pf is defined for that value.
Tests whether the argument (arg0) is a reference to the receiver object (this).
Tests whether the argument (arg0) is a reference to the receiver object (this).
The eq method implements an equivalence relation on
non-null instances of AnyRef, and has three additional properties:
x and y of type AnyRef, multiple invocations of
x.eq(y) consistently returns true or consistently returns false.x of type AnyRef, x.eq(null) and null.eq(x) returns false.null.eq(null) returns true. When overriding the equals or hashCode methods, it is important to ensure that their behavior is
consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they
should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).
true if the argument is a reference to the receiver object; false otherwise.
The equality method for reference types.
Returns true if this option is nonempty and the predicate
p returns true when applied to this Option's value.
Returns this Option if it is nonempty and applying the predicate p to
this Option's value returns true.
Returns this Option if it is nonempty and applying the predicate p to
this Option's value returns false.
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the finalize method is invoked, as
well as the interaction between finalize and non-local returns
and exceptions, are all platform dependent.
Returns the result of applying f to this Option's value if
this Option is nonempty.
Apply the given procedure f to the option's value,
if it is nonempty.
Apply the given procedure f to the option's value,
if it is nonempty. Otherwise, do nothing.
the procedure to apply.
flatMap
,map
A representation that corresponds to the dynamic class of the receiver object.
A representation that corresponds to the dynamic class of the receiver object.
The nature of the representation is platform dependent.
a representation that corresponds to the dynamic class of the receiver object.
Returns the option's value if the option is nonempty, otherwise
return the result of evaluating default.
Returns the option's value if the option is nonempty, otherwise
return the result of evaluating default.
the default expression.
The hashCode method for reference types.
Returns true if the option is an instance of Some, false otherwise.
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.
true if the receiver object is an instance of erasure of type T0; false otherwise.
Returns a singleton iterator returning the Option's value if it is nonempty, or an empty iterator if the option is empty.
Returns a Some containing the result of applying f to this Option's
value if this Option is nonempty.
Equivalent to !(this eq that).
Equivalent to !(this eq that).
true if the argument is not a reference to the receiver object; false otherwise.
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
Returns this Option if it is nonempty,
otherwise return the result of evaluating alternative.
Returns the option's value if it is nonempty,
or null if it is empty.
Returns the option's value if it is nonempty,
or null if it is empty.
Although the use of null is discouraged, code written to use
Option must often interface with code that expects and returns nulls.
val initalText: Option[String] = getInitialText val textField = new JComponent(initalText.orNull,20)
An iterator over all the elements of this product.
An iterator over all the elements of this product.
in the default implementation, an Iterator[Any]
A string used in the toString methods of derived classes.
A string used in the toString methods of derived classes.
Implementations may override this method to prepend a string prefix
to the result of toString methods.
in the default implementation, the empty string
Returns a Right containing the given
argument right if this is empty, or
a Left containing this Option's value
if this Option is nonempty.
Returns a singleton list containing the Option's value if it is nonempty, or the empty list if the Option is empty.
Returns a Left containing the given
argument left if this Option is empty, or
a Right containing this Option's value if
this is nonempty.
Creates a String representation of this object.
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
a String representation of the object.
Necessary to keep Option from being implicitly converted to
Iterable in for comprehensions.
use productIterator instead
Represents optional values. Instances of
Optionare either an instance of Some or the objectNone.The most idiomatic way to use an Option instance is to treat it as a collection or monad and use
map,flatMap,filter, orforeach:val name:Option[String] = request.getParameter("name") val upper = name map { _.trim } filter { _.length != 0 } map { _.toUpperCase } println(upper.getOrElse(""))Note that this is equivalent to
val upper = for { name <- request.getParameter("name") trimmed <- Some(name.trim) upper <- Some(trimmed.toUpperCase) if trimmed.length != 0 } yield upper println(upper.getOrElse(""))Because of how for comprehension works, if
Noneis returned fromrequest.getParameter, the entire expression results inNoneThis allows for sophisticated chaining of Option values without having to check for the existence of a value.
A less-idiomatic way to use Option values is via pattern matching:
val nameMaybe = request.getParameter("name") nameMaybe match { case Some(name) => { println(name.trim.toUppercase) } case None => { println("No name value") } }1.1, 16/01/2007