Java Stream map operation

Introduction

The following code shows how to use Stream map operation.

The square roots of the elements are first mapped to a new stream.

Then, reduce() is employed to compute the product. 

// Map one stream to another. 

import java.util.ArrayList;
import java.util.stream.Stream;

public class Main {

  public static void main(String[] args) {

    // A list of double values.
    ArrayList<Double> myList = new ArrayList<>();

    myList.add(7.0);/*from  ww w  .  ja  va2s .  co m*/
    myList.add(8.0);
    myList.add(10.0);
    myList.add(4.0);
    myList.add(17.0);
    myList.add(5.0);

    // Map the square root of the elements in myList to a new stream.
    Stream<Double> sqrtRootStrm = myList.stream().map((a) -> Math.sqrt(a));

    // Find the product to the square roots.
    double productOfSqrRoots = sqrtRootStrm.reduce(1.0, (a, b) -> a * b);

    System.out.println("Product of square roots is " + productOfSqrRoots);
  }
}



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