Example how to use Streams in Java 8+

Dieses kleine Programm zeigt wie man die Streams in Java8+ nutzen kann. Man kann mithilfe von Lambda Expressions Elemente aus Collections filtern, reduzieren und verändern. Nützlich um mehrere Funktionen zu meiden, das spart etliche Zeilen code.

This application is a short showcase how Streams in Java8+ works. You can filter, reduce and map elements with the help of lambda expressions from Collections. This is useful to avoid multiple functions.

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.stream.Collectors;

public class JavaStream {

    public JavaStream(){
        List<Integer> origin = new ArrayList<>(randomlistCreator());
        streamprocess(origin);
    }

    private List<Integer> randomlistCreator(){
        List<Integer> randomlist = new ArrayList<>();
        Random rn = new Random();
        rn.setSeed(System.currentTimeMillis());
        for(var n = 0; n < 50; n++){
            Integer i = rn.nextInt() % 210;
            randomlist.add(i);
        }
        return randomlist;
    }

    private void streamprocess(List<Integer> origin){
        origin
        .stream()
        .filter(elem -> elem % 2 == 0 && elem > 0)
        .map(elem -> (int) elem / 2)
        .collect(Collectors.toSet())
        .forEach(System.out::println);
    }

    public static void main(String[] args){
        new JavaStream();
    }  
}