Интерфейс Comparable

import java.util.Arrays;
public class Faculty implements Comparable{
    public int number;
    public String name;
    public String napravlenie;
 
    public Faculty (int number, String name,String napravlenie) {
        this.number= number;
        this.name = name;
        this.napravlenie = napravlenie;}
 
    /*Перегрузка метода compareTo */
    public int compareTo (Object obj)
    {
        Faculty temp = (Faculty) obj;
        if (this.number <temp.number) {
            return -1;}
        else
        if (this.number>temp.number){
            return 1;  }
        return 0;}
 
    public static void main (String [] args) {
 
        Faculty[] student = new Faculty[4];
        student[0] = new Faculty(1015, "Иванов", "filosof");
        student[1] = new Faculty(1024, "Петров", "filolog");
        student[2] = new Faculty(4563, "Сидоров", "math");
        student[3] = new Faculty(3473, "Семенов", "lingv");
 
        // Сортировка массива,
        Arrays.sort (student);
        for (int i=0; i<student.length; i++) {
            System.out.println (student [i].number+" " +student [i].name +" "+ student[i].napravlenie); }
    }
 
 
}

public int compareTo (Object obj)
    {
        Faculty temp = (Faculty) obj;
        if (this.name <temp.name) {
            return -1;}
        else
        if (this.name>temp.name){
            return 1;  }
        return 0;
}

import java.util.Arrays;
import java.util.Comparator;
 
public class Faculty
{
    static class FacultyName implements Comparator<Faculty> {
        public int compare(Faculty one, Faculty two) {
            return one.name.compareTo(two.name);
        }
    }
    static class FacultyNapravlenie implements Comparator<Faculty> {
        public int compare(Faculty one, Faculty two) {
            return one.napravlenie.compareTo(two.napravlenie);
        }
    }
    static class FacultyNumber implements Comparator<Faculty> {
        public int compare(Faculty one, Faculty two) {
            if (one.number < two.number) return -1;
            else if (one.number > two.number) return 1;
            return 0;
        }
    }
 
    public int number;
    public String name;
    public String napravlenie;
 
    public Faculty (int number, String name, String napravlenie) {
        this.number= number;
        this.name = name;
        this.napravlenie = napravlenie;}
 
 
    public static void main (String [] args) {
 
        Faculty[] student = new Faculty[4];
        student[0] = new Faculty(1015, "Сидоров", "filosof");
        student[1] = new Faculty(1024, "Петров", "filolog");
        student[2] = new Faculty(4563, "Иванов", "math");
        student[3] = new Faculty(3473, "Семенов", "lingv");
 
 
        Arrays.sort(student, new FacultyNapravlenie());
        for (int i = 0; i < student.length; i++) {
            System.out.println (student [i].number+" " +student [i].name +" "+ student[i].napravlenie); }
    }
 
 
}

Arrays.sort(student, new FacultyNapravlenie());