java TreeSet的使用

/*
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TreeSet:它可以给Set集合中的元素进行指定方式的排序。
?? ??? ?保证元素唯一性的方式：通过比较的结果是否为0.
?? ??? ?底层数据结构是：二叉树。
*/
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import java.util.*;  class TreeSetDemo3  {    public static void main(String[] args)      {        TreeSet ts = new TreeSet(new StudentComparatorByName());         ts.add(new Student("lisi0",30));        ts.add(new Student("lisixx",29));        ts.add(new Student("lisi9",29));        ts.add(new Student("lisi8",38));        ts.add(new Student("lisixx",29));        ts.add(new Student("lisi4",14));        //ts.add(new Student(39));        ts.add(new Student("lisi7",27));           System.out.println(ts);    }} class StudentComparatorByName implements Comparator{    public int compare(Object o1,Object o2)    {        Student s1 = (Student)o1;        Student s2 = (Student)o2;         int num = s1.getName().compareTo(s2.getName());        return num==0?new Integer(s1.getAge()).compareTo(new Integer(s2.getAge())):num;    }}  //同姓名同年龄的学生视为同一个学生。按照学生的年龄排序。class Student implements Comparable{    private int age;    private String name;    Student(String name,int age)    {        this.age = age;        this.name = name;    }     public int compareTo(Object obj)    {                Student stu = (Student)obj;                int num = new Integer(this.age).compareTo(new Integer(stu.age));         return num==0?this.name.compareTo(stu.name):num;         /*        if(this.age>stu.age)            return 1;        if(this.age==stu.age)            return this.name.compareTo(stu.name);        return -1;        */        /**/    }     public int getAge()    {        return age;    }    public String getName()    {        return name;    }    public String toString()    {        return name+"::"+age;    }} 

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