实现比较器有两种方法

第一种、一些类自己实现Comparable，笔试用的较少；

第二种、人为定义对类的比较。实现Comparator接口。

举例 有三个学生 我自创了学术类，mian生成了三个学生A\B\C要将他们按照id排序，在重新compare方法中，只要负数就放放前面，程序会自动帮你生成的。

import java.util.Arrays;
import java.util.Comparator;

import basic_class_01.Code_09_Comparator.Student;

public class Code_09_Comparator2 {

	public static class Student{
		String name;
		int id;
		int age;
		
		public Student(String name, int id, int age) {
			this.name = name;
			this.id = id;
			this.age = age;
		}
	}
	
	public static class IdComparator implements Comparator<Student>{

		@Override
		public int compare(Student o1, Student o2) {
			// TODO Auto-generated method stub
			return o1.id - o2.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("===========================");
	}
	public static void main(String[] args) {
		Student student1 = new Student("A", 9, 23);
		Student student2 = new Student("B", 2, 21);
		Student student3 = new Student("C", 3, 22);
		Student[] stus = new Student[] {student1,student2,student3};
		
		Arrays.sort(stus, new IdComparator());
		printStudents(stus);
	}

}