Student scores sorting help needed for Java

Question

import java.util.Scanner;
import java.util.Arrays;

class StudentScores {
public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.print("Enter the # of students");
    int numOfStudents = input.nextInt();
    int[] scores = new int[numOfStudents];
    String[] names = new String[numOfStudents];

    for (int i = 0; i < numOfStudents; i++) {
        input.nextLine();
        System.out.print("Enter name: ");
        names[i] = input.nextLine();
        System.out.print("Enter score: ");
        scores[i] = input.nextInt();
    }

                    // This doesn't sort anything, it just prints out the result in unsorted way
    /*for (int i = 0; i < numOfStudents; i++) {
        System.out.println(names[i] + " " + scores[i]);
    }*/

    Arrays.sort(scores);
    reverse(scores);


    for (int u: scores) {
        System.out.println(u);
    }
}

   public static int[] reverse(int[] array) {
    for (int i = 0, j = array.length - 1; i < j; i++, j--) {
        int temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }

    return array;
  }
 }

The original question is: Write a program that prompts the user to enter the number of students, the students’ names, and their scores, and prints student names in decreasing order of their scores.

My question is how do you display the name with the sorted list of scores?

You necessarily don't have to give me a complete solution, just give me a hint so I can solve it myself.

Answer 1

You can encapsulate the related fields into a class, e.g. a StudentRecord can encapsulate the fields name and score.

Now, you sort a collection of these objects based on the second field, score. When it comes time to print the sorted result, you iterate through the collection and print the first field, name.

To illustrate:

public class StudentRecord implements Comparable<StudentRecord> {

    private String name;
    private int score;

    public StudentRecord(String name, int score) {
        this.name = name;
        this.score = score;
    }

    @Override
    public int compareTo(StudentRecord other) {
        if (score == other.score) return 0;
        else if (score < other.score) return -1;
        else return 1;
    }

    @Override
    public String toString() {
        return name;
    }


    public static void main(String[] args) {

        StudentRecord stu1 = new StudentRecord("Matt", 50);
        StudentRecord stu2 = new StudentRecord("John", 90);

        if (stu1.compareTo(stu2) == 0) {
            System.out.println(stu1.toString() + " has the same score with " + stu2.toString());
        }
        else if (stu1.compareTo(stu2) < 0) {
            System.out.println(stu1.toString() + " has a lower score than " + stu2.toString());
        }
        else {
            System.out.println(stu1.toString() + " has a higher score than " + stu2.toString());
        }

        // output:
        // Matt has a lower score than John

    }

}

In many sorting algorithms, implementing the Comparable interface gives the algorithm enough information to sort a collection of such objects implementing said interface.

Answer 2

You're not going to be able to use Arrays.sort() for this problem because you need to sort both arrays together. Write a sorting function that sorts the scores in order, and every time it swaps two scores, swap the students with those scores as well.