Java Stream - 如何比较filter和map和foreach方法的线程名称

import java.util.Arrays;
import java.util.List;

public class Main {

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

    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()));

  }
}