How to sort user defined object in ArrayList

Question

Possible Duplicate:
How to sort an arraylist of objects by a property?

    public static void main(String args[]){

            List<Emp> unsortList = new ArrayList<Emp>();

            unsortList.add(new Emp(109));
            unsortList.add(new Emp(106));
            unsortList.add(new Emp(103));
            unsortList.add(new Emp(108));
            unsortList.add(new Emp(101));
    }

public class Emp {
Integer eid;
public Emp(Integer eid) {
    this.eid=eid;
}
}

Emp is user defined class & stored in ArrayList. How sort ArrayList.

Answer 1

Check out Collections#sort(List list, Comparator c)

It allows you supply your own Comparator which you can use to define how the objects will be matched

Answer 2

Implement Comparable<Emp> and use Collections.sort to sort the list

public class Emp implements Comparable<Emp> {
    Integer eid;

    public Emp(Integer eid) {
        this.eid = eid;
    }

    @Override
    public int compareTo(Emp o) {
        return eid.compareTo(o.eid);
    }
}