比较器整理

自己定义需要比较的东西

public class Bokeyuan {
    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 class IdAscendingComparator implements Comparator<Student>{//1.Id...自己定义的比较器；2.Comparator  继承接口，接口内放置自己定义的想要比较的东西；3.把定义好的类放到main函数的调用类上

        @Override
        public int compare(Student arg0, Student arg1) {
            // TODO 自动生成的方法存根
            return arg0.id-arg1.id;//怎么比较？？？1.当返回的数值为负数，前面的数值更小；2.返回的为正数，后面的参数更小，3.返回的为0，相等
        }        
    }
    public static class IdDescendingComparator implements Comparator<Student>{

        @Override
        public int compare(Student arg0, Student arg1) {
            // TODO 自动生成的方法存根
            return arg1.id-arg0.id;//降序
        }    
    }
    public static class AgeScendingComparator implements Comparator<Student>{

        @Override
        public int compare(Student arg0, Student arg1) {
            // TODO 自动生成的方法存根
            return arg0.age-arg1.age;//升序
        }        
    }
    public static class AgeDescendingComparator implements Comparator<Student>{

        @Override
        public int compare(Student arg0, Student arg1) {
            // TODO 自动生成的方法存根
            return arg1.age-arg0.age;//降序
        }        
    }
    public static void printStudent (Student[] students) {
        for(Student student:students) {//输出函数
            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",1,25);
        Student student2 =new Student("B",2,23);
        Student student3 =new Student("C",3,24);
        //建立数组，把学生1，2，3放进去
        Student[] students =new Student[] {
            student3,student2,student1
        };
        //Arrays.sort调用系统函数   有意义的情况：1.数组2.写入自己定义的比较器，不写的话，是单纯调用sort（students）按照内存地址排序毫无意义。例如，基础类型按照数值大小排序，从小到大。
        printStudent(students);
        Arrays.sort(students,new IdAscendingComparator());
        
        printStudent(students);
        Arrays.sort(students,new IdDescendingComparator());
        
        printStudent(students);
        Arrays.sort(students,new    AgeDescendingComparator());
        
        printStudent(students);
        Arrays.sort(students,new AgeScendingComparator());
        
            }
    }