Try

Companion object Try

sealed abstract class Try[+T] extends Product with Serializable

The Try type represents a computation that may fail during evaluation by raising an exception. It holds either a successfully computed value or the exception that was thrown. This is similar to the scala.util.Either type, but with different semantics.

Instances of Try[T] are an instance of either scala.util.Success[T] or scala.util.Failure[T].

For example, consider a computation that performs division on user-defined input. Try can reduce or eliminate the need for explicit exception handling in all of the places where an exception might be thrown.

Example:

import scala.io.StdIn
import scala.util.{Try, Success, Failure}

def divide: Try[Int] = {
  val dividend = Try(StdIn.readLine("Enter an Int that you'd like to divide:\n").toInt)
  val divisor = Try(StdIn.readLine("Enter an Int that you'd like to divide by:\n").toInt)
  val problem = dividend.flatMap(x => divisor.map(y => x/y))
  problem match {
    case Success(v) =>
      println("Result of " + dividend.get + "/"+ divisor.get +" is: " + v)
      Success(v)
    case Failure(e) =>
      println("You must've divided by zero or entered something that's not an Int. Try again!")
      println("Info from the exception: " + e.getMessage)
      divide
  }
}

An important property of Try shown in the above example is its ability to pipeline, or chain, operations, catching exceptions along the way. The flatMap and map combinators in the above example each essentially pass off either their successfully completed value, wrapped in the Success type for it to be further operated upon by the next combinator in the chain, or the exception wrapped in the Failure type usually to be simply passed on down the chain. Combinators such as recover and recoverWith are designed to provide some type of default behavior in the case of failure.

Note: only non-fatal exceptions are caught by the combinators on Try (see scala.util.control.NonFatal). Serious system errors, on the other hand, will be thrown.

Note:: all Try combinators will catch exceptions and return failure unless otherwise specified in the documentation.

Source: Try.scala

Linear Supertypes

java.io.Serializable, Product, Equals, AnyRef, Any

Known Subclasses

Failure, Success

Type Hierarchy

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Inherited

Try
Serializable
Product
Equals
AnyRef
Any

Implicitly

by any2stringadd
by StringFormat
by Ensuring
by ArrowAssoc

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Type Members

final class WithFilter extends AnyRef
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.

Abstract Value Members

abstract def canEqual(that: Any): Boolean
Checks whether this instance can possibly equal that.
Checks whether this instance can possibly equal that.
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.
that
the value being probed for possible equality
returns
true if this instance can possibly equal that, otherwise false
Definition Classes
Equals
abstract def collect[U](pf: PartialFunction[T, U]): Try[U]
Applies the given partial function to the value from this Success or returns this if this is a Failure.
abstract def failed: Try[Throwable]
Inverts this Try.
Inverts this Try. If this is a Failure, returns its exception wrapped in a Success. If this is a Success, returns a Failure containing an UnsupportedOperationException.
abstract def filter(p: (T) => Boolean): Try[T]
Converts this to a Failure if the predicate is not satisfied.
abstract def flatMap[U](f: (T) => Try[U]): Try[U]
Returns the given function applied to the value from this Success or returns this if this is a Failure.
abstract def flatten[U](implicit ev: <:<[T, Try[U]]): Try[U]
Transforms a nested Try, ie, a Try of type Try[Try[T]], into an un-nested Try, ie, a Try of type Try[T].
abstract def fold[U](fa: (Throwable) => U, fb: (T) => U): U
Applies fa if this is a Failure or fb if this is a Success.
Applies fa if this is a Failure or fb if this is a Success. If fb is initially applied and throws an exception, then fa is applied with this exception.
fa
the function to apply if this is a Failure
fb
the function to apply if this is a Success
returns
the results of applying the function
Example:
1. val result: Try[Int] = Try { string.toInt } log(result.fold( ex => "Operation failed with " + ex, v => "Operation produced value: " + v ))
abstract def foreach[U](f: (T) => U): Unit
Applies the given function f if this is a Success, otherwise returns Unit if this is a Failure.
Applies the given function f if this is a Success, otherwise returns Unit if this is a Failure.
Note: If f throws, then this method may throw an exception.
abstract def get: T
Returns the value from this Success or throws the exception if this is a Failure.
abstract def getOrElse[U >: T](default: => U): U
Returns the value from this Success or the given default argument if this is a Failure.
Returns the value from this Success or the given default argument if this is a Failure.
Note:: This will throw an exception if it is not a success and default throws an exception.
abstract def isFailure: Boolean
Returns true if the Try is a Failure, false otherwise.
abstract def isSuccess: Boolean
Returns true if the Try is a Success, false otherwise.
abstract def map[U](f: (T) => U): Try[U]
Maps the given function to the value from this Success or returns this if this is a Failure.
abstract def orElse[U >: T](default: => Try[U]): Try[U]
Returns this Try if it's a Success or the given default argument if this is a Failure.
abstract def productArity: Int
The size of this product.
The size of this product.
returns
for a product A(x₁, ..., x_k), returns k
Definition Classes
Product
abstract def productElement(n: Int): Any
The n^th element of this product, 0-based.
The n^th element of this product, 0-based. In other words, for a product A(x₁, ..., x_k), returns x_(n+1) where 0 <= n < k.
n
the index of the element to return
returns
the element n elements after the first element
Definition Classes
Product
Exceptions thrown
IndexOutOfBoundsException if the n is out of range(n < 0 || n >= productArity).
abstract def recover[U >: T](pf: PartialFunction[Throwable, U]): Try[U]
Applies the given function f if this is a Failure, otherwise returns this if this is a Success.
Applies the given function f if this is a Failure, otherwise returns this if this is a Success. This is like map for the exception.
abstract def recoverWith[U >: T](pf: PartialFunction[Throwable, Try[U]]): Try[U]
Applies the given function f if this is a Failure, otherwise returns this if this is a Success.
Applies the given function f if this is a Failure, otherwise returns this if this is a Success. This is like flatMap for the exception.
abstract def toEither: Either[Throwable, T]
Returns Left with Throwable if this is a Failure, otherwise returns Right with Success value.
abstract def toOption: Option[T]
Returns None if this is a Failure or a Some containing the value if this is a Success.
abstract def transform[U](s: (T) => Try[U], f: (Throwable) => Try[U]): Try[U]
Completes this Try by applying the function f to this if this is of type Failure, or conversely, by applying s if this is a Success.

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
AnyRef → Any
final def ##: Int
Equivalent to x.hashCode except for boxed numeric types and null.
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.
returns
a hash value consistent with ==
Definition Classes
AnyRef → Any
def +(other: String): String
Implicit
This member is added by an implicit conversion from Try[T] toany2stringadd[Try[T]] performed by method any2stringadd in scala.Predef.
Definition Classes
any2stringadd
def ->[B](y: B): (Try[T], B)
Implicit
This member is added by an implicit conversion from Try[T] toArrowAssoc[Try[T]] performed by method ArrowAssoc in scala.Predef.
Definition Classes
ArrowAssoc
Annotations
@inline()
final def ==(arg0: Any): Boolean
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
The expression x == that is equivalent to if (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
AnyRef → Any
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 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.
Definition Classes
Any
Exceptions thrown
ClassCastException if the receiver object is not an instance of the erasure of type T0.
def clone(): AnyRef
Create a copy of the receiver object.
Create a copy of the receiver object.
The default implementation of the clone method is platform dependent.
returns
a copy of the receiver object.
Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.CloneNotSupportedException]) @native()
Note
not specified by SLS as a member of AnyRef
def ensuring(cond: (Try[T]) => Boolean, msg: => Any): Try[T]
Implicit
This member is added by an implicit conversion from Try[T] toEnsuring[Try[T]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
def ensuring(cond: (Try[T]) => Boolean): Try[T]
Implicit
This member is added by an implicit conversion from Try[T] toEnsuring[Try[T]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
def ensuring(cond: Boolean, msg: => Any): Try[T]
Implicit
This member is added by an implicit conversion from Try[T] toEnsuring[Try[T]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
def ensuring(cond: Boolean): Try[T]
Implicit
This member is added by an implicit conversion from Try[T] toEnsuring[Try[T]] performed by method Ensuring in scala.Predef.
Definition Classes
Ensuring
final def eq(arg0: AnyRef): Boolean
Tests whether the argument (that) is a reference to the receiver object (this).
Tests whether the argument (that) 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:
- It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
- For any non-null instance 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).
returns
true if the argument is a reference to the receiver object; false otherwise.
Definition Classes
AnyRef
def equals(arg0: AnyRef): Boolean
The equality method for reference types.
The equality method for reference types. Default implementation delegates to eq.
See also equals in scala.Any.
returns
true if the receiver object is equivalent to the argument; false otherwise.
Definition Classes
AnyRef → Any
def finalize(): Unit
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.
Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.Throwable])
Note
not specified by SLS as a member of AnyRef
final 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
AnyRef → Any
Annotations
@native()
def hashCode(): Int
The hashCode method for reference types.
The hashCode method for reference types. See hashCode in scala.Any.
returns
the hash code value for this object.
Definition Classes
AnyRef → Any
Annotations
@native()
final def isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object has the same erasure as T0.
Test whether the dynamic type of the receiver object has the same erasure as T0.
Depending on what T0 is, the test is done in one of the below ways:
- T0 is a non-parameterized class type, e.g. BigDecimal: this method returns true if the value of the receiver object is a BigDecimal or a subtype of BigDecimal.
- T0 is a parameterized class type, e.g. List[Int]: this method returns true if the value of the receiver object is some List[X] for any X. For example, List(1, 2, 3).isInstanceOf[List[String]] will return true.
- T0 is some singleton type x.type or literal x: this method returns this.eq(x). For example, x.isInstanceOf[1] is equivalent to x.eq(1)
- T0 is an intersection X with Y or X & Y: this method is equivalent to x.isInstanceOf[X] && x.isInstanceOf[Y]
- T0 is a union X | Y: this method is equivalent to x.isInstanceOf[X] || x.isInstanceOf[Y]
- T0 is a type parameter or an abstract type member: this method is equivalent to isInstanceOf[U] where U is T0's upper bound, Any if T0 is unbounded. For example, x.isInstanceOf[A] where A is an unbounded type parameter will return true for any value of x.
This is exactly equivalent to the type pattern _: T0
returns
true if the receiver object is an instance of erasure of type T0; false otherwise.
Definition Classes
Any
Note
due to the unexpectedness of List(1, 2, 3).isInstanceOf[List[String]] returning true and x.isInstanceOf[A] where A is a type parameter or abstract member returning true, these forms issue a warning.
final def ne(arg0: AnyRef): Boolean
Equivalent to !(this eq that).
Equivalent to !(this eq that).
returns
true if the argument is not a reference to the receiver object; false otherwise.
Definition Classes
AnyRef
final def notify(): Unit
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.
Definition Classes
AnyRef
Annotations
@native()
Note
not specified by SLS as a member of AnyRef
final def notifyAll(): Unit
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.
Definition Classes
AnyRef
Annotations
@native()
Note
not specified by SLS as a member of AnyRef
def productElementName(n: Int): String
The name of the n^th element of this product, 0-based.
The name of the n^th element of this product, 0-based. In the default implementation, an empty string.
n
the index of the element name to return
returns
the name of the specified element
Definition Classes
Product
Exceptions thrown
IndexOutOfBoundsException if the n is out of range(n < 0 || n >= productArity).
def productElementNames: Iterator[String]
An iterator over the names of all the elements of this product.
An iterator over the names of all the elements of this product.
Definition Classes
Product
def productIterator: Iterator[Any]
An iterator over all the elements of this product.
An iterator over all the elements of this product.
returns
in the default implementation, an Iterator[Any]
Definition Classes
Product
def productPrefix: String
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.
returns
in the default implementation, the empty string
Definition Classes
Product
final def synchronized[T0](arg0: => T0): T0
Executes the code in body with an exclusive lock on this.
Executes the code in body with an exclusive lock on this.
returns
the result of body
Definition Classes
AnyRef
def toString(): String
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.
returns
a String representation of the object.
Definition Classes
AnyRef → Any
final def wait(): Unit
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait--.
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait--.
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException])
Note
not specified by SLS as a member of AnyRef
final def wait(arg0: Long, arg1: Int): Unit
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-int-
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-int-
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException])
Note
not specified by SLS as a member of AnyRef
final def wait(arg0: Long): Unit
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-.
See https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-.
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException]) @native()
Note
not specified by SLS as a member of AnyRef
final def withFilter(p: (T) => Boolean): WithFilter
Creates a non-strict filter, which eventually converts this to a Failure if the predicate is not satisfied.
Creates a non-strict filter, which eventually converts this to a Failure if the predicate is not satisfied.
Note: unlike filter, withFilter does not create a new Try. Instead, it restricts the domain of subsequent map, flatMap, foreach, and withFilter operations.
As Try is a one-element collection, this may be a bit overkill, but it's consistent with withFilter on Option and the other collections.
p
the predicate used to test elements.
returns
an object of class WithFilter, which supports map, flatMap, foreach, and withFilter operations. All these operations apply to those elements of this Try which satisfy the predicate p.
Annotations
@inline()

Deprecated Value Members

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 for String.format (@see java.lang.String.format).
Implicit
This member is added by an implicit conversion from Try[T] toStringFormat[Try[T]] performed by method StringFormat in scala.Predef.
Definition Classes
StringFormat
Annotations
@deprecated @inline()
Deprecated
(Since version 2.12.16) Use formatString.format(value) instead of value.formatted(formatString), or use the f"" string interpolator. In Java 15 and later, formatted resolves to the new method in String which has reversed parameters.
def →[B](y: B): (Try[T], B)
Implicit
This member is added by an implicit conversion from Try[T] toArrowAssoc[Try[T]] 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.

Packages

Package structure

Automatic imports

Try

Companion object Try

sealed abstract class Try[+T] extends Product with Serializable

Type Members

Abstract Value Members

Concrete Value Members

Deprecated Value Members

Inherited from java.io.Serializable

Inherited from Product

Inherited from Equals

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd fromTry[T] to any2stringadd[Try[T]]

Inherited by implicit conversion StringFormat fromTry[T] to StringFormat[Try[T]]

Inherited by implicit conversion Ensuring fromTry[T] to Ensuring[Try[T]]

Inherited by implicit conversion ArrowAssoc fromTry[T] to ArrowAssoc[Try[T]]

Ungrouped

Packages

Package structure

Automatic imports

Try

Companion object Try

sealed abstract class Try[+T] extends Product with Serializable

Type Members

Abstract Value Members

Concrete Value Members

Deprecated Value Members

Inherited from java.io.Serializable

Inherited from Product

Inherited from Equals

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd fromTry[T] to any2stringadd[Try[T]]

Inherited by implicit conversion StringFormat fromTry[T] to StringFormat[Try[T]]

Inherited by implicit conversion Ensuring fromTry[T] to Ensuring[Try[T]]

Inherited by implicit conversion ArrowAssoc fromTry[T] to ArrowAssoc[Try[T]]

Ungrouped

Try