[SPARK-27323] Use Single-Abstract-Method support in Scala 2.12 to simplify code

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.0.0
• Fix Version/s: 3.0.0
• Component/s: GraphX, Spark Core, SQL, Structured Streaming
• Target Version/s: 3.0.0
• Assignee: Sean R. Owen
• Reporter: Sean R. Owen
• Created: 29/Mar/19 18:03
• Updated: 02/Apr/19 17:57
• Resolved: 02/Apr/19 14:38

Description

Scala 2.12 supports Single Abstract Method (SAM) syntax like Java 8. Using this would lightly simplify a lot of code where we define an anonymous inner class. E.g.

private[sql] val ordering = new Ordering[InternalType] {
    override def compare(x: Array[Byte], y: Array[Byte]): Int = {
      TypeUtils.compareBinary(x, y)
    }
  }

becomes:

  private[sql] val ordering = (x: Array[Byte], y: Array[Byte]) => TypeUtils.compareBinary(x, y)

There's a small improvement to readability, and probably a tiny benefit at runtime as these become lambdas in the JVM, not inner classes that have to be compiled and instantiated. (There's also a very small reduction in the chance that those inner classes are accidentally holding references to things we don't want them to.)

Issue Links

• links to: GitHub Pull Request #24241