Streams12.java

package com.winterbe.java8.samples.stream;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.UUID;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.TimeUnit;

/**
 * @author Benjamin Winterberg
 */
public class Streams12 {

    public static void main(String[] args) {
        List<String> strings = Arrays.asList("a1", "a2", "b1", "c2", "c1");

//        test1();
//        test2(strings);
        test3(strings);
//        test4();
    }

    private static void test4() {
        List<String> values = new ArrayList<>(100);
        for (int i = 0; i < 100; i++) {
            UUID uuid = UUID.randomUUID();
            values.add(uuid.toString());
        }

        // sequential

        long t0 = System.nanoTime();

        long count = values
            .parallelStream()
            .sorted((s1, s2) -> {
                System.out.format("sort:    %s <> %s [%s]\n", s1, s2, Thread.currentThread().getName());
                return s1.compareTo(s2);
            })
            .count();
        System.out.println(count);

        long t1 = System.nanoTime();

        long millis = TimeUnit.NANOSECONDS.toMillis(t1 - t0);
        System.out.println(String.format("parallel sort took: %d ms", millis));
    }

    private static void test3(List<String> strings) {
        strings
            .parallelStream()
            .filter(s -> {
                System.out.format("filter:  %s [%s]\n", s, Thread.currentThread().getName());
                return true;
            })
            .map(s -> {
                System.out.format("map:     %s [%s]\n", s, Thread.currentThread().getName());
                return s.toUpperCase();
            })
            .sorted((s1, s2) -> {
                System.out.format("sort:    %s <> %s [%s]\n", s1, s2, Thread.currentThread().getName());
                return s1.compareTo(s2);
            })
            .forEach(s -> System.out.format("forEach: %s [%s]\n", s, Thread.currentThread().getName()));
    }

    private static void test2(List<String> strings) {
        strings
            .parallelStream()
            .filter(s -> {
                System.out.format("filter:  %s [%s]\n", s, Thread.currentThread().getName());
                return true;
            })
            .map(s -> {
                System.out.format("map:     %s [%s]\n", s, Thread.currentThread().getName());
                return s.toUpperCase();
            })
            .forEach(s -> System.out.format("forEach: %s [%s]\n", s, Thread.currentThread().getName()));
    }

    private static void test1() {
        // -Djava.util.concurrent.ForkJoinPool.common.parallelism=5

        ForkJoinPool commonPool = ForkJoinPool.commonPool();
        System.out.println(commonPool.getParallelism());
    }
}