（一）、自定义比较器Comparator及其使用

        比较器Comparator用途：当面试算法时，前面的排序不是考察重点时，直接用JDK封装的排序算法。

Arrays.sort(对象数组，new 自定义的比较器()) ；

public class CustomComparator {

    public static class Student {
        public String name;
        public int id;
        public int age;

        public Student(String name, int id, int age) {
            this.name = name;
            this.id = id;
            this.age = age;
        }
    }

    
    public static void main(String[] args) {
        Student student1 = new Student("A", 1, 23);
        Student student2 = new Student("B", 2, 21);
        Student student3 = new Student("C", 3, 22);

        Student[] students = new Student[] { student3, student2, student1 };
        printStudents(students);

        //数组排序
        Arrays.sort(students, new IdAscendingComparator());
        printStudents(students);

        Arrays.sort(students, new IdDescendingComparator());
        printStudents(students);
        //也可以用堆排序，优先队列就是堆
        PriorityQueue heap = new PriorityQueue<>(new IdDescendingComparator());
        heap.add(student3);
        heap.add(student1);
        heap.add(student2);
        while (!heap.isEmpty()) {
            Student student = heap.poll();
            System.out.println("Name: " + student.name + ", Id: " + student.id + ", Age: " + student.age);
        }


    }

    
    public static class IdAscendingComparator implements Comparator {
        @Override
        public int compare(Student o1, Student o2) {
            return o1.id - o2.id;
        }
    }

    
    public static class IdDescendingComparator implements Comparator {
        @Override
        public int compare(Student o1, Student o2) {
            return o2.id - o1.id;
        }
    }

    public static void printStudents(Student[] students) {
        for (Student student : students) {
            System.out.println("Name : " + student.name + ", Id : " + student.id + ", Age : " + student.age);
        }
        System.out.println("===========================");
    }



}