Comparable:::::Sort an object using comparable

package Coparable_Std;
//Sort an object using comparable

import java.util.ArrayList;
import java.util.*;

public class Runner_Student_Comparable
{

public static void main(String[] args)
{

Student_Comparable sc1 = new Student_Comparable(12,"maths","Michle");
Student_Comparable sc2 = new Student_Comparable(100,"Science","Hitler");
Student_Comparable sc3 = new Student_Comparable(67,"hindi","Dicosta");
Student_Comparable sc4 = new Student_Comparable(99,"Urdu","Hillary");
Student_Comparable sc5 = new Student_Comparable(10,"Marathi","Donald");

ArrayList al = new ArrayList();
al.add(sc1);
al.add(sc2);
al.add(sc3);
al.add(sc4);
al.add(sc5);
Collections.sort(al); // Yaha se internally compareTo() call hota hai..[Comparable (I)]

Iterator itr = al.iterator();
while(itr.hasNext())
{
Student_Comparable sc = (Student_Comparable)itr.next();
System.out.println(sc.name +" ~ " +sc.roll+" ~ "+sc.subject);
}


}

}

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package Coparable_Std;

import java.util.ArrayList;

public class Student_Comparable implements Comparable<Student_Comparable>

{

int roll;

String subject;

String name;

Student_Comparable(int a, String b, String c)

{

this.roll = a;

this.subject = b;

this.name = c;

}

public int compareTo(Student_Comparable sc) 

{

//System.out.println("Inside compareTo()");

if(roll == sc.roll)

{

return 0;

}

if(roll > sc.roll)

{

return -1;

}

else

return 1;

}

}