Question

我正在编写代码以按年龄对人员列表进行排序，并以年龄最大的人为前缀并打印出来

定义的对象列表：

    Person person1 = new Person(40,"John", "Smith");
    Person person2 = new Person(45,"Mike", "Well");
    Person person3 = new Person(68,"Bob", "Parks");
    Person person4 = new Person(49,"Leon", "Foo");
    Person person5 = new Person(30,"Christian", "Markus");

    List<Person> personList = new ArrayList<>();
    personList.add(person1);
    personList.add(person2);
    personList.add(person3);
    personList.add(person4);
    personList.add(person5);

我可以对其进行排序和添加前缀，但问题是要获取第一项并打印出来

    List<Person> orderedPersonAge  = personList
            .stream()
            .sorted(Comparator.comparing(Person::getAge).reversed())
            .map(s-> new 
    Person(s.getAge(),"Super"+s.getName(),s.getSureName()))
            .collect(Collectors.toList());
    System.out.println(orderedPersonAge);

我尝试过使用findFirst（）...

不同的方法是按年龄排序，取最早的，然后添加前缀...

Answer 1

你可以做

Person orderedPersonAge  = personList
        .stream()
        .sorted(Comparator.comparing(Person::getAge).reversed())
        .map(s-> new Person(s.getAge(),"Super"+s.getName(),s.getSureName()))
        .collect(Collectors.toList())
        .get(0);
System.out.println(orderedPersonAge);

或

Person orderedPersonAge  = personList
        .stream()
        .sorted(Comparator.comparing(Person::getAge).reversed())
        .map(s-> new Person(s.getAge(),"Super"+s.getName(),s.getSureName()))
        .findFirst()
        .get();
System.out.println(orderedPersonAge);

Answer 2

您可能正在寻找

personList.stream()
   .max(Comparator.comparing(Person::getAge)) // solves for sort with reverse and find first
   .map(s -> new Person(s.getAge(), "Super" + s.getName(), s.getSurname())) // map if present
   .ifPresent(System.out::println); // print the mapped output if present

排序对象流，并首先打印出来

2 个答案: