@Test //定制排序   public void testTreeSet2(){    //1.创建一个实现Comparator接口的匿名类对象    Comparator com = new Comparator(){        //向TreeSet中添加Student类的对象，在此compare方法中，指明是按照Customer的哪个属性排序的        public int compare(Object o1,Object o2){            if(o1 instanceof Student && o2 instanceof Student ){                Student s1 = (Student)o1;                Student s2 = (Student)o2;                int i = s1.getId()-s2.getId();                if(i==0){                    return s1.getName().compareTo(s2.getName());                }                else{                    return i;                }            }            return 0;        }    };    //2.将此对象作为形参传递给TreeSet的构造器中    TreeSet set = new TreeSet(com);    //3.向TreeSet中添加compare方法中所涉及的类对象    set.add(new Student(001,"shang"));    set.add(new Student(005,"sfdg"));    set.add(new Student(006,"shdsf"));    set.add(new Student(031,"xvz"));    set.add(new Student(031,"adf"));    //set.add(new Student(031,"adf"));    System.out.println(set.size());    System.out.println(set);}