Apache-Spark : What is map(_._2) shorthand for?

Question

I read a project\'s source code, found:

val sampleMBR = inputMBR.map(_._2).sample

inputMBR is a tuple.

the function

Answer 1

I have found the solutions.

First the underscore here is as placeholder.

To make a function literal even more concise, you can use underscores as placeholders for one or more parameters, so long as each parameter appears only one time within the function literal.

See more about underscore in Scala at What are all the uses of an underscore in Scala?.