20175324数据结构-排序

针对下面的Student类，使用Comparator编程完成以下功能：

1. 在测试类StudentTest中新建学生列表，包括自己和学号前后各两名学生，共5名学生,给出运行结果（排序前，排序后）
2. 对这5名同学分别用学号和总成绩进行增序排序，提交两个Comparator的代码
3. 课下提交代码到码云

import java.util.Comparator;
public class IDComparator implements Comparator {
@Override
public int compare(Object o1, Object o2) {
Student st1 = (Student)o1;
Student st2 = (Student)o2;
return (Integer.parseInt(st1.getId())-Integer.parseInt(st2.getId()));
}
}

import java.util.Comparator;
public class scoreComparator implements Comparator {
@Override
public int compare(Object o1, Object o2) {
Student st1 = (Student)o1;
Student st2 = (Student)o2;
return (int) (st1.getTotalScore()-st2.getTotalScore());
}
}

在数据结构和算法中，排序是很重要的操作，要让一个类可以进行排序，有两种方法：

• 有类的源代码，针对某一成员变量排序，让类实现Comparable接口,调用Collection.sort(List)
• 没有类的源代码，或者多种排序，新建一个类，实现Comparator接口 调用Collection.sort(List, Compatator)

class Student {
   private String id;//表示学号
   private String name;//表示姓名
   private int age;//表示年龄
   private double computer_score;//表示计算机课程的成绩
   private double english_score;//表示英语课的成绩
   private double maths_score;//表示数学课的成绩
   private double total_score;// 表示总成绩
   private double ave_score; //表示平均成绩

   public Student(String id, String name){
       this.id = id;
       this.name = name;
}
   public Student(String id, String name, char sex, int age){
       this(id, name);
       this.sex = sex;
       this.age = age;
}
   public String getId(){
       return id;
}//获得当前对象的学号，
   public double getComputer_score(){
       return computer_score;
}//获得当前对象的计算机课程成绩,
   public double getMaths_score(){
       return maths_score;
}//获得当前对象的数学课程成绩,
   public double getEnglish_score(){
       return english_score;
}//获得当前对象的英语课程成绩,

   public void setId(String id){
       this.id=id;
}// 设置当前对象的id值,
   public void setComputer_score(double computer_score){
       this.computer_score=computer_score;
}//设置当前对象的Computer_score值,
   public void setEnglish_score(double english_score){
       this.english_score=english_score;
}//设置当前对象的English_score值,
   public void setMaths_score(double maths_score){
       this.maths_score=maths_score;
}//设置当前对象的Maths_score值,

   public double getTotalScore(){
       return computer_score+maths_score+english_score;
}// 计算Computer_score, Maths_score 和English_score 三门课的总成绩。
   public double getAveScore(){
       return getTotalScore()/3;
}// 计算Computer_score, Maths_score 和English_score 三门课的平均成绩。

}

class Undergraduate extends Student{
   private String classID;

   public Undergraduate(String id, String name, char sex, int age,String classID){
       super(id,name,sex,age);
       this.classID=classID;
   }
   public String getClassID(){
       return classID;
   }
   public void setClassID(String classID){
       this.classID=classID;
   }
}

ComparatorByID.java

import java.util.Comparator;
import java.util.*;
public class ComparatorByID implements Comparator<Student> {
    @Override
    public int compare(Student o1, Student o2)
    {
        return Integer.parseInt(o1.getId()) - Integer.parseInt(o2.getId());
    }
}

ComparatorByMark.java

import java.util.Comparator;
public class ComparatorByMark implements Comparator<Student> {
    @Override
    public int compare(Student stu1, Student stu2){
        return (int)(stu1.getTotalScore()-stu2.getTotalScore());
    }
}