how to sort the arraylist of objects in java

1package beginnersbook.com;
2import java.util.*;
3public class Details  {
4
5	public static void main(String args[]){
6	   ArrayList<Student> arraylist = new ArrayList<Student>();
7	   arraylist.add(new Student(101, "Zues", 26));
8	   arraylist.add(new Student(505, "Abey", 24));
9	   arraylist.add(new Student(809, "Vignesh", 32));
10
11	   /*Sorting based on Student Name*/
12	   System.out.println("Student Name Sorting:");
13	   Collections.sort(arraylist, Student.StuNameComparator);
14
15	   for(Student str: arraylist){
16			System.out.println(str);
17	   }
18
19	   /* Sorting on Rollno property*/
20	   System.out.println("RollNum Sorting:");
21	   Collections.sort(arraylist, Student.StuRollno);
22	   for(Student str: arraylist){
23			System.out.println(str);
24	   }
25	}
26}

1package beginnersbook.com;
2import java.util.Comparator;
3public class Student  {
4    private String studentname;
5    private int rollno;
6    private int studentage;
7
8    public Student(int rollno, String studentname, int studentage) {
9        this.rollno = rollno;
10        this.studentname = studentname;
11        this.studentage = studentage;
12    }
13    ...
14    //Getter and setter methods same as the above examples
15    ...
16    /*Comparator for sorting the list by Student Name*/
17    public static Comparator<Student> StuNameComparator = new Comparator<Student>() {
18
19	public int compare(Student s1, Student s2) {
20	   String StudentName1 = s1.getStudentname().toUpperCase();
21	   String StudentName2 = s2.getStudentname().toUpperCase();
22
23	   //ascending order
24	   return StudentName1.compareTo(StudentName2);
25
26	   //descending order
27	   //return StudentName2.compareTo(StudentName1);
28    }};
29
30    /*Comparator for sorting the list by roll no*/
31    public static Comparator<Student> StuRollno = new Comparator<Student>() {
32
33	public int compare(Student s1, Student s2) {
34
35	   int rollno1 = s1.getRollno();
36	   int rollno2 = s2.getRollno();
37
38	   /*For ascending order*/
39	   return rollno1-rollno2;
40
41	   /*For descending order*/
42	   //rollno2-rollno1;
43   }};
44    @Override
45    public String toString() {
46        return "[ rollno=" + rollno + ", name=" + studentname + ", age=" + studentage + "]";
47    }
48
49}