import java.util.Arrays;

import java.util.Comparator;

public class Comparator1 {

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 IdAscendingComprator implements Comparator<Student> {

@Override

public int compare(Student o1, Student o2) {

return o1.id - o2.id;

// 等价于：

// if (o1.id < o2.id) {

// return -1;

// }

// else if (o1.id > o2.id) {

// return 1;

// }

// else {return 0;}

}

}

public static class IdDescendingComparator implements Comparator<Student> {

@Override

public int compare(Student o1, Student o2) {

return o2.id - o1.id;

}

}

public static class AgeAscendingComparator implements Comparator<Student> {

@Override

public int compare(Student o1, Student o2) {

return o1.age - o2.age;

}

}

public static class AgeDescendingComparator implements Comparator<Student> {

@Override

public int compare(Student o1, Student o2) {

return o2.age - o1.age;

}

}

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 s1 = new Student("A", 1, 23);

Student s2 = new Student("B", 2, 21);

Student s3 = new Student("C", 3, 22);

Student[] students = new Student[] {s1, s2, s3};

printStudents(students);

Arrays.sort(students, new IdAscendingComprator());

printStudents((students));

Arrays.sort(students, new IdDescendingComparator());

printStudents(students);

Arrays.sort(students, new AgeAscendingComparator());

printStudents(students);

Arrays.sort(students, new AgeDescendingComparator());

printStudents(students);

}

}