java 重写compareTo方法实现类排序

class expert implements Comparable<expert> {       private int age;    public expert(int age) {    this.age = age;    }          public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }@Overridepublic int compareTo(expert e) {return this.age - e.getAge();}}public class test03 {public static void main(String [] args){expert e1 = new expert(1);expert e2 = new expert(2);expert e3 = new expert(3);ArrayList<expert> list = new ArrayList<expert>();list.add(e3);list.add(e2);list.add(e1);Collections.sort(list);for(expert li:list){System.out.print(li.getAge());}}}

collections.sort方法使用的是归并排序java6，timesortjava7