TreeSet集合内部排序

import java.util.*;/*    TreeSet集合内部实现了排序    1. 自定义对象需要实现Comparable接口的compareTo方法，自定义排序规则,return 1（第一个元素大于第二个元素），0（相等），-1（小于） 【正数负数均可，不一定要是1或者-1】    2. 如果元素本身的排序规则不适用，那么自定义比较器实现Comparator接口，并在初始化集合的时传入。    3. 底层数据结构是二叉树，大于放右边，小于放左边*/class TreeSetDemo {    public static void main(String[] args) {        TreeSet ts = new TreeSet(new Mycompare());        // ts.add(new People("张三",3));        // ts.add(new People("赵一",9));     //  ts.add(new People("李四",4));        // ts.add(new People("王五",5));        // ts.add(new People("李四四",4));        ts.add(new People("a02",3));        ts.add(new People("a01",5));        ts.add(new People("a39",9));        ts.add(new People("a40",7));        System.out.println(ts);        Iterator i = ts.iterator();        while(i.hasNext()) {            People p = (People) i.next();            System.out.println(p.getName() + "....." + p.getAge());        }    }}// 元素类实现Comparable接口，复写compareTo方法class People implements Comparable {    private String name;    private int age;    People (String name, int age) {        this.name = name;        this.age = age;    }    public String getName() {        return this.name;    }    public int getAge(){        return this.age;    }     public int compareTo (Object obj) {        People p = (People) obj;        if (this.age > p.age) {            return 1;        } else if (this.age == p.age){            return this.name.compareTo(p.name);        }        return -1;    }}// 比较器实现Comparator接口，复写compare方法class Mycompare implements Comparator {    public int compare(Object o1, Object o2) {        People p1 = (People) o1;        People p2 = (People) o2;        int num = p1.getName().compareTo(p2.getName());        if (num == 0) {            return p1.getAge() - p2.getAge();        }        return num;    }}