Map(3)--treeMap的排序

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当key是Student类对象，value是String型时，
（一）在Student类中重写compareTo方法

    @Overridepublic int compareTo(student o) {    int num=this.age-o.age;    return num==0?this.name.compareTo(o.name):num;}

回到主函数，

    public static void demo1() {    TreeMap<student,String> tm=new TreeMap<student,String>();    tm.put(new student("张三",23), "北京");    tm.put(new student("赵六",13), "上海");    tm.put(new student("李四",24), "广州");    tm.put(new student("王五",25), "深圳");    System.out.println(tm);}

（二）传入比较器Comparator《E》

    public static void demo2() {    TreeMap<student,String> tm=new TreeMap<student,String>(            new Comparator<student>(){                @Override                public int compare(student s1, student s2) {                    int num=s1.getName().compareTo(s2.getName());                    return num==0?s1.getAge()-s2.getAge():num;                }            });    tm.put(new student("张三",23), "北京");    tm.put(new student("赵六",13), "上海");    tm.put(new student("李四",24), "广州");    tm.put(new student("王五",25), "深圳");    System.out.println(tm);}

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