java - 如何以正确的方式过滤 ArrayList 的内容？

Question

我正在寻找一种更好的方法来过滤 ArrayList 的内容

例如，这个程序有一个名为“students”的主ArrayList，然后我根据该列表的内容创建了其他子列表(oldStudents、youngStudents、stupidStudents、smartStudents)。目标是根据学生的用户选择过滤ArrayList (年轻、年长、聪明或愚蠢)

    ArrayList<String> students = new ArrayList<String>(); 
    ArrayList<String> smartStudents = new ArrayList<String>(); 
    ArrayList<String> stupidStudents = new ArrayList<String>(); 
    ArrayList<String> oldStudents = new ArrayList<String>(); 
    ArrayList<String> youngStudents = new ArrayList<String>(); 


    //adding all the students to students list 
    Collections.addAll(students, "Ram", "Mohan", "Sohan", "Rabi", "Shabbir","Jack", "Johnson", "Peter", "Despina", "Me");
    //adding young students to youngStudents list 
    Collections.addAll(youngStudents, "Ram", "Mohan", "Sohan", "Rabi", "Shabbir");
    //adding smart students to oldStudents list 
    Collections.addAll(oldStudents, "Jack", "Johnson", "Peter", "Despina", "Me");
    //adding smart students to smartStudents list 
    Collections.addAll(smartStudents, "Sohan", "Rabi", "Peter", "Despina");
    //adding smart students to stupidStudents list 
    Collections.addAll(stupidStudents, "Ram", "Mohan", "Shabbir","Jack", "Johnson", "Me");

    Scanner input = new Scanner(System.in);
    String uInput = "";



    System.out.print("This is a students search engine, write 'young' for younger students and 'old' for older ones ");
    uInput = input.nextLine();

    if(uInput.equals("young")) {

        students.removeAll(oldStudents); 

    } else if (uInput.equals("old")) {

        students.removeAll(youngStudents);

    }


    System.out.print("now write 'Smart' for smarter students and 'Stupid' for less smart students ");
    uInput = input.nextLine();

  if(uInput.equals("smart")) {

        students.removeAll(stupidStudents); 

    } else if (uInput.equals("Stupid")) {

        students.removeAll(smartStudents);

    }


  System.out.println(students);

它正在起作用，但我相信有更好的方法来实现这一目标

Answer 1

您可以使用这种方法:

class Student { String name; boolean old; boolean stupid; }

List<Student> students = initializeListOfStudents();

// alter these flags accordingly to your needs
Boolean old = null;
Boolean stupid = true;

// then do the filter
List<Student> allStupids = students.stream()
    .filter(it -> (old==null || it.old == old) && (stupid==null || it.stupid==stupid))
    .collect(Collectors.toList());