import java.util.*;
import java.util.function.*;

/** Iteration.
 * @author Jaanus Poeial
 * @since 1.8
 */
public class J8example1 {

  static int sum = 0;  // hack to make sum final for bad examples

  public static void main (String[] args) {

    // find sum of positive elements in the list
    List<Integer> myList = Arrays.asList (1, -1, 0, 2, -4, -5);


    // old way (Java 1)
    sum = 0;
    for (int i = 0; i < myList.size(); i++) {
      if (myList.get(i) > 0) {
        sum += myList.get (i);
      }
    }
    System.out.println ("SumPos is: " + sum);


    // little better old way (Java 5)
    sum = 0;
    for (int elem : myList) {
      if (elem > 0) {
        sum += elem;
      }
    }
    System.out.println ("SumPos is: " + sum);


    // Java 8 forEach and anonymous Consumer (ugly)
    sum = 0;
    myList.forEach (new Consumer<Integer>() {
        public void accept (Integer elem) {
          if (elem > 0) {
            sum += elem;
          }
        }
      });
    System.out.println ("SumPos is: " + sum);


    // Java 8 forEach and lambda expression
    sum = 0;
    myList.forEach (elem -> {
        if (elem > 0) {
          sum += elem;
        }
      });
    System.out.println ("SumPos is: " + sum);


    // Java 8 stream, filter, reduce (with lambda expression) - the best
    sum = myList.stream()
                .filter (elem -> (elem > 0))
                .reduce (0, (s, e) -> s + e);
    System.out.println ("SumPos is: " + sum);
    
    
    // Arrays can also be converted to streams
    System.out.println ("another sum is: " +
        Arrays.stream (new int[]{1,2,-3,-3,-4})
        .filter (elem -> elem<0)
        .sum()        		
    );

  }
}