有没有办法使用 lambda 表达式比较器对多个条件进行排序

Question

I am trying to sort an array of students by various criteria.I want to sort by their first name and if that is the same then by their last name. If both names are the same then by an ID number. I am currently using a lambda expression which successfully sorts them by their first name. Is there a way to pass the other sorting criteria to the expression? (There are getter methods similar to getFirstName() for the ID and the last name). I have written a generic quicksort algorithm to which I pass my custom comparator interface, IStudentComparator. This is my code for the first criteria:

QuickSort<Student> myNameSort = new QuickSort<>();
IStudentComparator compare = (Student a, Student b) 
    -> (a.getFirstName().compareTo(b.getFirstName()) < 0);
        
myNameSort.quickSort(myStudents,0,myStudents.length-1,compare); 

Answer 1

What stops you from using the fields in your comparator?

IStudentComparator compare (Student a, Student b) -> {
  // compare first name
  // compare last name if first name was equal
  // return comparison of ID number if last name was equal
}

Answer 2

Here is a small class file that depicts how you can use a lambda expression to sort a list of objects by multiple properties.

Java 8 has the method thenComparing with the help of which you can compare by multiple properties.

public class SortByMultiple {

    public static void main(String[] args) {
        ArrayList<Employee> employees = getUnsortedEmployeeList();

        //Compare by first name and then last name id
        Comparator<Employee> compareByName = Comparator
                .comparing(Employee::getId)
                .thenComparing(Employee::getLastName)
                .thenComparing(Employee::getFirstName);

        List<Employee> sortedEmployees = employees.stream()
                .sorted(compareByName)
                .collect(Collectors.toList());

        System.out.println(sortedEmployees);
    }

    private static ArrayList<Employee> getUnsortedEmployeeList() {
        ArrayList<Employee> list = new ArrayList<>();
        list.add(new Employee(1l, "Alex", "Gussin"));
        list.add(new Employee(4l, "Brian", "Sux"));
        list.add(new Employee(5l, "Neon", "Piper"));
        return list;
    }

    public static class Employee {

        Long id;
        String firstName;
        String lastName;

        public Long getId() {
            return id;
        }

        public void setId(Long id) {
            this.id = id;
        }

        public String getFirstName() {
            return firstName;
        }

        public void setFirstName(String firstName) {
            this.firstName = firstName;
        }

        public String getLastName() {
            return lastName;
        }

        public void setLastName(String lastName) {
            this.lastName = lastName;
        }

        public Employee(Long id, String firstName, String lastName) {
            this.id = id;
            this.firstName = firstName;
            this.lastName = lastName;
        }

        @Override
        public String toString() {
            return "Employee{" + "id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + '}';
        }
    }
}