Scala 3/API/scala.jdk.javaapi/CollectionConverters

CollectionConverters

object CollectionConverters extends AsJavaConverters with AsScalaConverters

This object contains methods that convert between Scala and Java collections.

This object contains methods that convert between Scala and Java collections.

The explicit conversion methods defined here are intended to be used in Java code. For Scala code, it is recommended to use the extension methods defined in scala.jdk.CollectionConverters.

Note: to create Java Streams that operate on Scala collections (sequentially or in parallel), use StreamConverters.

// Java Code
import scala.jdk.javaapi.CollectionConverters;
public class A {
  public void t(scala.collection.immutable.List l) {
    java.util.List jl = CollectionConverters.asJava(l);
  }
}

The conversions return adapters for the corresponding API, i.e., the collections are wrapped, not converted. Changes to the original collection are reflected in the view, and vice versa.

The following conversions are supported via asScala and asJava:

scala.collection.Iterable       <=> java.lang.Iterable
scala.collection.Iterator       <=> java.util.Iterator
scala.collection.mutable.Buffer <=> java.util.List
scala.collection.mutable.Set    <=> java.util.Set
scala.collection.mutable.Map    <=> java.util.Map
scala.collection.concurrent.Map <=> java.util.concurrent.ConcurrentMap

The following conversions are supported via asScala and through specially-named methods to convert to Java collections, as shown:

scala.collection.Iterable    <=> java.util.Collection   (via asJavaCollection)
scala.collection.Iterator    <=> java.util.Enumeration  (via asJavaEnumeration)
scala.collection.mutable.Map <=> java.util.Dictionary   (via asJavaDictionary)

In addition, the following one-way conversions are provided via asJava:

scala.collection.Seq         => java.util.List
scala.collection.mutable.Seq => java.util.List
scala.collection.Set         => java.util.Set
scala.collection.Map         => java.util.Map

The following one way conversion is provided via asScala:

java.util.Properties => scala.collection.mutable.Map

In all cases, converting from a source type to a target type and back again will return the original source object.

class Object
trait Matchable
class Any

Value members

Inherited methods

def asJava[K, V](m: Map[K, V]): ConcurrentMap[K, V]

Converts a Scala mutable concurrent.Map to a Java ConcurrentMap.

Converts a Scala mutable concurrent.Map to a Java ConcurrentMap.

The returned Java ConcurrentMap is backed by the provided Scala concurrent.Map and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala concurrent.Map was previously obtained from an implicit or explicit call of asScala then the original Java ConcurrentMap will be returned.

Value Params
m

The Scala concurrent.Map to be converted.

Returns

A Java ConcurrentMap view of the argument.

Inherited from
AsJavaConverters
def asJava[K, V](m: Map[K, V]): Map[K, V]

Converts a Scala Map to a Java Map.

Converts a Scala Map to a Java Map.

The returned Java Map is backed by the provided Scala Map and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala Map was previously obtained from an implicit or explicit call of asScala then the original Java Map will be returned.

Value Params
m

The Scala Map to be converted.

Returns

A Java Map view of the argument.

Inherited from
AsJavaConverters
def asJava[K, V](m: Map[K, V]): Map[K, V]

Converts a Scala mutable Map to a Java Map.

Converts a Scala mutable Map to a Java Map.

The returned Java Map is backed by the provided Scala Map and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala Map was previously obtained from an implicit or explicit call of asScala then the original Java Map will be returned.

Value Params
m

The Scala mutable Map to be converted.

Returns

A Java Map view of the argument.

Inherited from
AsJavaConverters
def asJava[A](s: Set[A]): Set[A]

Converts a Scala Set to a Java Set.

Converts a Scala Set to a Java Set.

The returned Java Set is backed by the provided Scala Set and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala Set was previously obtained from an implicit or explicit call of asScala then the original Java Set will be returned.

Value Params
s

The Scala Set to be converted.

Returns

A Java Set view of the argument.

Inherited from
AsJavaConverters
def asJava[A](s: Set[A]): Set[A]

Converts a Scala mutable Set to a Java Set.

Converts a Scala mutable Set to a Java Set.

The returned Java Set is backed by the provided Scala Set and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala Set was previously obtained from an implicit or explicit call of asScala then the original Java Set will be returned.

Value Params
s

The Scala mutable Set to be converted.

Returns

A Java Set view of the argument.

Inherited from
AsJavaConverters
def asJava[A](s: Seq[A]): List[A]

Converts a Scala Seq to a Java List.

Converts a Scala Seq to a Java List.

The returned Java List is backed by the provided Scala Seq and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala Seq was previously obtained from an implicit or explicit call of asScala then the original Java List will be returned.

Value Params
s

The Scala Seq to be converted.

Returns

A Java List view of the argument.

Inherited from
AsJavaConverters
def asJava[A](s: Seq[A]): List[A]

Converts a Scala mutable Seq to a Java List.

Converts a Scala mutable Seq to a Java List.

The returned Java List is backed by the provided Scala Seq and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala Seq was previously obtained from an implicit or explicit call of asScala then the original Java List will be returned.

Value Params
s

The Scala Seq to be converted.

Returns

A Java List view of the argument.

Inherited from
AsJavaConverters
def asJava[A](b: Buffer[A]): List[A]

Converts a Scala mutable Buffer to a Java List.

Converts a Scala mutable Buffer to a Java List.

The returned Java List is backed by the provided Scala Buffer and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala Buffer was previously obtained from an implicit or explicit call of asScala then the original Java List will be returned.

Value Params
b

The Scala Buffer to be converted.

Returns

A Java List view of the argument.

Inherited from
AsJavaConverters
def asJava[A](i: Iterable[A]): Iterable[A]

Converts a Scala Iterable to a Java Iterable.

Converts a Scala Iterable to a Java Iterable.

The returned Java Iterable is backed by the provided Scala Iterable and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala Iterable was previously obtained from an implicit or explicit call of asScala then the original Java Iterable will be returned.

Value Params
i

The Scala Iterable to be converted.

Returns

A Java Iterable view of the argument.

Inherited from
AsJavaConverters
def asJava[A](i: Iterator[A]): Iterator[A]

Converts a Scala Iterator to a Java Iterator.

Converts a Scala Iterator to a Java Iterator.

The returned Java Iterator is backed by the provided Scala Iterator and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala Iterator was previously obtained from an implicit or explicit call of asScala then the original Java Iterator will be returned.

Value Params
i

The Scala Iterator to be converted.

Returns

A Java Iterator view of the argument.

Inherited from
AsJavaConverters
def asJavaCollection[A](i: Iterable[A]): Collection[A]

Converts a Scala Iterable to an immutable Java Collection.

Converts a Scala Iterable to an immutable Java Collection.

If the Scala Iterable was previously obtained from an implicit or explicit call of asScala then the original Java Collection will be returned.

Value Params
i

The Scala Iterable to be converted.

Returns

A Java Collection view of the argument.

Inherited from
AsJavaConverters
def asJavaDictionary[K, V](m: Map[K, V]): Dictionary[K, V]

Converts a Scala mutable Map to a Java Dictionary.

Converts a Scala mutable Map to a Java Dictionary.

The returned Java Dictionary is backed by the provided Scala Dictionary and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala Map was previously obtained from an implicit or explicit call of asScala then the original Java Dictionary will be returned.

Value Params
m

The Scala Map to be converted.

Returns

A Java Dictionary view of the argument.

Inherited from
AsJavaConverters
def asJavaEnumeration[A](i: Iterator[A]): Enumeration[A]

Converts a Scala Iterator to a Java Enumeration.

Converts a Scala Iterator to a Java Enumeration.

The returned Java Enumeration is backed by the provided Scala Iterator and any side-effects of using it via the Java interface will be visible via the Scala interface and vice versa.

If the Scala Iterator was previously obtained from an implicit or explicit call of asScala then the original Java Enumeration will be returned.

Value Params
i

The Scala Iterator to be converted.

Returns

A Java Enumeration view of the argument.

Inherited from
AsJavaConverters
def asScala(p: Properties): Map[String, String]

Converts a Java Properties to a Scala mutable Map[String, String].

Converts a Java Properties to a Scala mutable Map[String, String].

The returned Scala Map[String, String] is backed by the provided Java Properties and any side-effects of using it via the Scala interface will be visible via the Java interface and vice versa.

Value Params
p

The Java Properties to be converted.

Returns

A Scala mutable Map[String, String] view of the argument.

Inherited from
AsScalaConverters
def asScala[A, B](d: Dictionary[A, B]): Map[A, B]

Converts a Java Dictionary to a Scala mutable Map.

Converts a Java Dictionary to a Scala mutable Map.

The returned Scala Map is backed by the provided Java Dictionary and any side-effects of using it via the Scala interface will be visible via the Java interface and vice versa.

If the Java Dictionary was previously obtained from an implicit or explicit call of asJavaDictionary then the original Scala Map will be returned.

Value Params
d

The Java Dictionary to be converted.

Returns

A Scala mutable Map view of the argument.

Inherited from
AsScalaConverters
def asScala[A, B](m: ConcurrentMap[A, B]): Map[A, B]

Converts a Java ConcurrentMap to a Scala mutable ConcurrentMap.

Converts a Java ConcurrentMap to a Scala mutable ConcurrentMap.

The returned Scala ConcurrentMap is backed by the provided Java ConcurrentMap and any side-effects of using it via the Scala interface will be visible via the Java interface and vice versa.

If the Java ConcurrentMap was previously obtained from an implicit or explicit call of asJava then the original Scala ConcurrentMap will be returned.

Value Params
m

The Java ConcurrentMap to be converted.

Returns

A Scala mutable ConcurrentMap view of the argument.

Inherited from
AsScalaConverters
def asScala[A, B](m: Map[A, B]): Map[A, B]

Converts a Java Map to a Scala mutable Map.

Converts a Java Map to a Scala mutable Map.

The returned Scala Map is backed by the provided Java Map and any side-effects of using it via the Scala interface will be visible via the Java interface and vice versa.

If the Java Map was previously obtained from an implicit or explicit call of asJava then the original Scala Map will be returned.

If the wrapped map is synchronized (e.g. from java.util.Collections.synchronizedMap), it is your responsibility to wrap all non-atomic operations with underlying.synchronized. This includes get, as java.util.Map's API does not allow for an atomic get when null values may be present.

Value Params
m

The Java Map to be converted.

Returns

A Scala mutable Map view of the argument.

Inherited from
AsScalaConverters
def asScala[A](s: Set[A]): Set[A]

Converts a Java Set to a Scala mutable Set.

Converts a Java Set to a Scala mutable Set.

The returned Scala Set is backed by the provided Java Set and any side-effects of using it via the Scala interface will be visible via the Java interface and vice versa.

If the Java Set was previously obtained from an implicit or explicit call of asJava then the original Scala Set will be returned.

Value Params
s

The Java Set to be converted.

Returns

A Scala mutable Set view of the argument.

Inherited from
AsScalaConverters
def asScala[A](l: List[A]): Buffer[A]

Converts a Java List to a Scala mutable Buffer.

Converts a Java List to a Scala mutable Buffer.

The returned Scala Buffer is backed by the provided Java List and any side-effects of using it via the Scala interface will be visible via the Java interface and vice versa.

If the Java List was previously obtained from an implicit or explicit call of asJava then the original Scala Buffer will be returned.

Value Params
l

The Java List to be converted.

Returns

A Scala mutable Buffer view of the argument.

Inherited from
AsScalaConverters
def asScala[A](c: Collection[A]): Iterable[A]

Converts a Java Collection to a Scala Iterable.

Converts a Java Collection to a Scala Iterable.

If the Java Collection was previously obtained from an implicit or explicit call of asJavaCollection then the original Scala Iterable will be returned.

Value Params
c

The Java Collection to be converted.

Returns

A Scala Iterable view of the argument.

Inherited from
AsScalaConverters
def asScala[A](i: Iterable[A]): Iterable[A]

Converts a Java Iterable to a Scala Iterable.

Converts a Java Iterable to a Scala Iterable.

The returned Scala Iterable is backed by the provided Java Iterable and any side-effects of using it via the Scala interface will be visible via the Java interface and vice versa.

If the Java Iterable was previously obtained from an implicit or explicit call of asJava then the original Scala Iterable will be returned.

Value Params
i

The Java Iterable to be converted.

Returns

A Scala Iterable view of the argument.

Inherited from
AsScalaConverters
def asScala[A](e: Enumeration[A]): Iterator[A]

Converts a Java Enumeration to a Scala Iterator.

Converts a Java Enumeration to a Scala Iterator.

The returned Scala Iterator is backed by the provided Java Enumeration and any side-effects of using it via the Scala interface will be visible via the Java interface and vice versa.

If the Java Enumeration was previously obtained from an implicit or explicit call of asJavaEnumeration then the original Scala Iterator will be returned.

Value Params
e

The Java Enumeration to be converted.

Returns

A Scala Iterator view of the argument.

Inherited from
AsScalaConverters
def asScala[A](i: Iterator[A]): Iterator[A]

Converts a Java Iterator to a Scala Iterator.

Converts a Java Iterator to a Scala Iterator.

The returned Scala Iterator is backed by the provided Java Iterator and any side-effects of using it via the Scala interface will be visible via the Java interface and vice versa.

If the Java Iterator was previously obtained from an implicit or explicit call of asJava then the original Scala Iterator will be returned.

Value Params
i

The Java Iterator to be converted.

Returns

A Scala Iterator view of the argument.

Inherited from
AsScalaConverters