相当于Scala视图的Groovy

Question

I am trying to convert this Scala code to Groovy:

val r = BigInt(2).pow(1000).toString.view.map(_.asDigit).sum

What is the equivalent of "view" to groovy?

Answer 1

Java8 brings chars() (basically an iterator), which you can reduce over for the sum:

groovy:000> 2G.pow(1000).toString().chars().reduce(0){ a,b -> a+b-48 }
===> 1366

Or closer to your Scala code (map, sum):

groovy:000> 2G.pow(1000).toString().chars().map{ it-48 }.sum()
===> 1366

That magic 48 is the ascii for "0".

As a generic answer: Many of the functional methods in groovy tend to realize the results, but Java 8 streams are just as easy to use from Groovy.

Answer 2

def result = new BigInteger(2).pow(1000).toString().toCharArray().toList().sum { it - 48 }

要么

def result1 = 2g.pow(1000).toString().toCharArray().toList().sum { it - 48 }