How to use an array of objects and call them in methods in Java

1. class Student 
2. { 
3. private String name; 
4. private int roll; 
5.  
6. public void setName(String name) 
7. { 
8. this.name=name; 
9. } 
10. public void setRoll(int roll) 
11. { 
12. this.roll=roll; 
13. } 
14. public String getName() 
15. { 
16. return name; 
17. } 
18. public int getRoll() 
19. { 
20. return roll; 
21. } 
22. } 
23. ------------------------------------------------------------- 
24. import java.io.*; 
25. class Department 
26. { 
27. public static void main(String args[]) 
28. { 
29. BufferedReader br=new BufferefReader(new InputStreamReader(System.in)); 
30. System.out.println("How many elements you want to create in the array?"); 
31. int n=Integer.parseInt(br.readLine()); 
32.  
33. Student students[]=new Student[n]; //Creating array of object of Student class 
34.  
35. for(int i=0;i
36. { 
37. students[i]=new Student(); //Instantiation of object 
38. System.out.println("Enter name"); 
39. String na=br.readLine(); 
40. System.out.println("Enter roll"); 
41. int r=Integer.parseInt(br.readLine()); 
42. students[i].setName(na); 
43. students[i].setRoll(r); 
44. } 
45. Department obj=new Department(); 
46. obj.displayDetails(students); 
47. } 
48.  
49. public void displayDetails(Student[] s) 
50. { 
51. for(Student stu:s) 
52. { 
53. System.out.println("Name: "+stu.getName()); 
54. System.out.println("Roll: "+stu.getRoll()); 
55. } 
56. } 
57. }