Is there an implicit method to convert scala.collection.mutable.StringBuilder to java.lang.StringBuilder?
I am using a Java library (JCommander) in which one of the methods (usage) takes a java.jang.StringBuilder argument.
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3 Answers
You can't start with a Scala StringBuilder and then obtain the Java version. You can, however, wrap a java.lang.StringBuilder in the Scala version. So:
val jsb = new java.lang.StringBuilder();
val sb = new StringBuilder(jsb);
// Do Scala-y stuff with sb
JCommander.whatever.usage(jsb);
// Do more Scala-y stuff
Since--not a guarantee, but true in practice right now (2.8, 2.9)--the Scala wrapper doesn't store any state (instead just referring to the Java version), you're safe to mix and match usage of the two.
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Looking at the source code, it seems there's absolutely no way to get a java.lang.StringBuilder from a scala.collection.mutable.StringBuilder.
You can create a new java.lang.StringBuilder with Scala's, going through a conversion of some type (String or CharSequence).
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Use this implicit transform do do this:
implicit def b2b(b: scala.collection.mutable.StringBuilder) =
new java.lang.StringBuilder(b)
1 Comment
Ralph
Actually, I don't think that will work. I presume that any Java method that expects a
java.lang.StringBuilder expects to modify it and allow the caller access to those changes. The implicit method you show creates a "defensive" copy of the scala.collection.mutable.StringBuilder. Any changes in the called method will not be reflected in the scala.collection.mutable.StringBuilder. Now that I think about it, the only way it could be implemented is if scala.collection.mutable.StringBuilder extended or wrapped java.lang.StringBuilder.