I have two files. One is scala and other is java.
Scala file has a function which returns scala immutable map.
Java file wants to use that map as dictionary.
I am a newbie to scala and java. How can I convert that scala map to java dicionary?
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Is your project in Java or Scala?Enrico Susatyo– Enrico Susatyo2014-02-01 06:59:11 +00:00Commented Feb 1, 2014 at 6:59
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Its in scala. I am using sbt for buildK.K– K.K2014-02-01 07:03:46 +00:00Commented Feb 1, 2014 at 7:03
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1As a note, you should never use Dictionary or Hashtable in new code unless interfacing with ancient code that requires it. Use the Map interface (and usually HashMap) instead.chrylis -cautiouslyoptimistic-– chrylis -cautiouslyoptimistic-2014-02-01 08:18:14 +00:00Commented Feb 1, 2014 at 8:18
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2 Answers
This is a better way to convert a Scala immutable.Map to a Java Map in Java.
java.util.Map<String, String> javaMap = scala.collection.JavaConverters
.mapAsJavaMapConverter(scalaMap).asJava();
Comments
Use the static forwarders from Java. In Scala 2.13 the API is simplified, with overloaded asJava for conversion to Java:
$ javap -cp ~/scala-2.13.0/lib/scala-library.jar scala.jdk.javaapi.CollectionConverters
Compiled from "CollectionConverters.scala"
public final class scala.jdk.javaapi.CollectionConverters {
public static scala.collection.mutable.Map<java.lang.String, java.lang.String> asScala(java.util.Properties);
public static <A, B> scala.collection.mutable.Map<A, B> asScala(java.util.Dictionary<A, B>);
public static <A, B> scala.collection.concurrent.Map<A, B> asScala(java.util.concurrent.ConcurrentMap<A, B>);
public static <A, B> scala.collection.mutable.Map<A, B> asScala(java.util.Map<A, B>);
public static <A> scala.collection.mutable.Set<A> asScala(java.util.Set<A>);
public static <A> scala.collection.mutable.Buffer<A> asScala(java.util.List<A>);
public static <A> scala.collection.Iterable<A> asScala(java.util.Collection<A>);
public static <A> scala.collection.Iterable<A> asScala(java.lang.Iterable<A>);
public static <A> scala.collection.Iterator<A> asScala(java.util.Enumeration<A>);
public static <A> scala.collection.Iterator<A> asScala(java.util.Iterator<A>);
public static <K, V> java.util.concurrent.ConcurrentMap<K, V> asJava(scala.collection.concurrent.Map<K, V>);
public static <K, V> java.util.Map<K, V> asJava(scala.collection.Map<K, V>);
public static <K, V> java.util.Dictionary<K, V> asJavaDictionary(scala.collection.mutable.Map<K, V>);
public static <K, V> java.util.Map<K, V> asJava(scala.collection.mutable.Map<K, V>);
public static <A> java.util.Set<A> asJava(scala.collection.Set<A>);
public static <A> java.util.Set<A> asJava(scala.collection.mutable.Set<A>);
public static <A> java.util.List<A> asJava(scala.collection.Seq<A>);
public static <A> java.util.List<A> asJava(scala.collection.mutable.Seq<A>);
public static <A> java.util.List<A> asJava(scala.collection.mutable.Buffer<A>);
public static <A> java.util.Collection<A> asJavaCollection(scala.collection.Iterable<A>);
public static <A> java.lang.Iterable<A> asJava(scala.collection.Iterable<A>);
public static <A> java.util.Enumeration<A> asJavaEnumeration(scala.collection.Iterator<A>);
public static <A> java.util.Iterator<A> asJava(scala.collection.Iterator<A>);
}
Given a Scala class that returns a Scala Map:
$ jshell --class-path .:~/scala-2.13.0/lib/scala-library.jar
| Welcome to JShell -- Version 11.0.3
| For an introduction type: /help intro
jshell> Map<String, String> vs = scala.jdk.javaapi.CollectionConverters.asJava(new mytools.MapMaker().m())
vs ==> {greeting=hi, reply=bye}
