Comparator와 compare을 이용한다. import java.util.Arrays; import java.util.Collections; import java.util.Comparator; import java.util.ArrayList; public class Main { static class Student{ String name; Integer score; Integer input_ranks; } public static void main(String[] args) { ArrayList students = new ArrayList(); Collections.sort(students, new Comparator() { public int compare(Student s1, Student s2..