按年级排序列表学生

Question

I have a exercise OOP. Define abstract class Human with first name and last name. Define new class Student which is derived from Human and has new field – grade. Define class Worker derived from Human with new property WeekSalary and WorkHoursPerDay and method MoneyPerHour() that returns money earned by hour by the worker. Define the proper constructors and properties for this hierarchy. Initialize a list of 10 students and sort them by grade in ascending order. Initialize a list of 10 workers and sort them by money per hour in descending order. Merge the lists and sort them by first name and last name.

I have create classes: Human, Student, and Worker. Now I want to sort list Student by Grade. What should I code in java ?

package Exercise2;

import java.util.*;

public class Main {

    public static void main(String[] args) {

        List<Student> students = Arrays.asList(
                new Student("Tam","Le Trung Ngoc ", "2011"), 
                new Student("Thai","Le Hoang Thai ", "2012"), 
                new Student("Phuong", "Vu Thi Thu ","2011"), 
                new Student("Nguyen", "Tran ", "2013"), 
                new Student("Hoang", "Pham Minh ", "2009"), 
                new Student("Tri","Truong Hoang ", "2011"), 
                new Student("Tuan", "Nguyen Anh ","2015"), 
                new Student("Tai", "Le Minh ", "2015"), 
                new Student("Cuong", "Nguyen Manh ", "2012"), 
                new Student("An","Pham Phuoc ", "2011"));
        System.out.println("------------STUDENTS------------");
        System.out.println(students);

        System.out.println("------------WORKERS------------");

        List<Worker> workers = Arrays.asList(
                new Worker("An","Le Minh ",150,8),
                new Worker("Hai","Nguyen Thanh ",200,4),
                new Worker("Lan","Nguyen Thi ",350,12),
                new Worker("A","Nguyen Van ",150,5),
                new Worker("Lua","Tran Thi Kim ",150,4),
                new Worker("Tu","Nguyen Thanh ",125,6),
                new Worker("Phong","Le Trung ",375,8),
                new Worker("Trang","Nguyen Thi Yen ",500,8),
                new Worker("Thien","Le Ngoc ",1500,8),
                new Worker("Vu","Le ",150,8)
                );
        System.out.println(workers);
    }

}

Answer 1

In an effort not to solve your homework for you I'm not going to post the code. but you need to look at how you will overload the compare() method in these different subclasses of human. That way depending on what is being compared you can sort them on name, grade, or salary.

Answer 2

Use a Comparator when sorting the collection:

Collections.sort(students, (Student o1, Student o2) -> {
  return o1.getGrade().compareTo(o2.getGrade()); // Tune this to your needs
});

If you are not using Java 8 you must use the (old-fashioned) new Comparator instead of the lambda expression.

Answer 3

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace _2DArrays
{
    class Program
    {
        static void Main(string[] args)
        {
            //try
            //{ 
            int p;
            do
            {
                Console.WriteLine("Enter Student number");
                int s = Convert.ToInt32(Console.ReadLine());
                Console.WriteLine("Enter Course number");
                int c = Convert.ToInt32(Console.ReadLine());
                string[] name = new string[s];
                double[] GPA = new double[s];
                string[] course = new string[c];
                int[] Chr = new int[c];
                double[,] score = new double[s, c];
                double[,] gradevalue = new double[s, c];
                string[,] grade = new string[s, c];
                double[] copyGPA = new double[c];
                for (int i = 0; i < c; i++)
                {
                    Console.WriteLine("Enter  " + (i + 1) + " course");
                    course[i] = Console.ReadLine();
                    Console.WriteLine("Enter  " + course[i] + " course credit hour");
                    Chr[i] = Convert.ToInt32(Console.ReadLine());

                }
                Console.Clear();
                for (int i = 0; i < s; i++)
                {
                    Console.WriteLine("Enter  " + (i + 1) + "  student name");
                    name[i] = Console.ReadLine();
                    double g = 0;
                    int ch = 0;
                    for (int j = 0; j < c; j++)
                    {
                        Console.WriteLine("Enter  " + course[j] + " course score for  " + name[i]);
                        score[i, j] = Convert.ToDouble(Console.ReadLine());
                        if (score[i, j] >= 85)
                        {
                            grade[i, j] = "A";
                            gradevalue[i, j] = 4;
                        }
                        else if (score[i, j] >= 70)
                        {
                            grade[i, j] = "B";
                            gradevalue[i, j] = 3;
                        }
                        else if (score[i, j] >= 60)
                        {
                            grade[i, j] = "C";
                            gradevalue[i, j] = 2;
                        }
                        else
                        {
                            grade[i, j] = "D";
                            gradevalue[i, j] = 1;
                        }
                        ch = ch + Chr[j];
                        g = g + (gradevalue[i, j] * Chr[j]);
                    }
                    GPA[i] = g / ch;
                }
                //GPA=(copyGPA, 0);
                //Array.Sort();
                Console.Clear();
                for (int i = 0; i < s; i++)
                {
                    Console.WriteLine("\t\t\t\tSTUDENT'S GRADE REPORT SHEET @ 2020");
                    Console.WriteLine("________________________________STUDENT NAME:   " + name[i] +"________________________");


                    Console.WriteLine("COURSE\t\tCHOUR\t\tSCORE\t\tGRADE\t\tGVALUE");
                    for (int j = 0; j < c; j++)
                    {


                        Console.WriteLine(course[j] + "\t\t" + Chr[j] + "\t\t" + score[i, j] + "\t\t" + grade[i, j] + "\t\t" + gradevalue[i, j]);

                    }
                    // Console.WriteLine("GPA:" + GPA[i]);
                    Console.WriteLine("________________________________GPA:   " + GPA[i] +"________________________________\n\n");
                }


                Console.WriteLine("IF YOU WANT TO TRY AGAIN PRESS 1");
                p = Convert.ToInt32(Console.ReadLine());
                Console.Clear();
            } while (p == 1);

            Console.ReadKey();

        }
    }
}