JAVA compareTo实现treeSet()排序

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package test.treeset;import java.util.Iterator;import java.util.Set;import java.util.TreeSet;public class test_treeset {     @SuppressWarnings("unchecked")    public static void main(String[] args) {            Set ts = new TreeSet();            ts.add(new Teacher("zhangsan", 1));            ts.add(new Teacher("lisi", 2));            ts.add(new Teacher("wangmazi", 3));            ts.add(new Teacher("wangwu",4));            ts.add(new Teacher("mazi", 3));            Iterator it = ts.iterator();            while (it.hasNext()) {                System.out.println(it.next());            }        }}class Teacher implements Comparable {    int num;    String name;    Teacher(String name, int num) {        this.num = num;        this.name = name;    }    public String toString() {        return "学号：" + num + "\t\t姓名：" + name;    }    //o中存放时的红黑二叉树中的节点，从根节点开始比较    public int compareTo(Object o) {        Teacher ss = (Teacher) o;        int result = num < ss.num ? 1 : (num == ss.num ? 0 : -1);//降序        //int result = num > ss.num ? 1 : (num == ss.num ? 0 : -1);//升序        if (result == 0) {            result = name.compareTo(ss.name);        }        return result;    }}
运行结果：
学号：4 姓名：wangwu
学号：3 姓名：mazi
学号：3 姓名：wangmazi
学号：2 姓名：lisi
学号：1 姓名：zhangsan
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