Java Stream - 如何map和filter带有自定义函数的字符串

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class Main {
  public static void main(String[] args) {

    List<String> names = Arrays.asList("CSS", "CSS3", "HTML", "Java",
        "Javascript", "Oracle", "MySQL");

    String name5 = names.stream().map(Main::toUpperCase)
        .filter(Main::greaterThanFive).limit(2)
        .collect(Collectors.joining(" + ")).toString()
        + " = WSM!!!";

    System.out.println(name5);
  }

  private static String toUpperCase(String s) {
    System.out.println("toUpperCase: " + s);
    return s.toUpperCase();
  }

  private static boolean greaterThanFive(String s) {
    System.out.println("greaterThanFive: " + s);
    return s.length() > 5;
  }
}