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2D Array, best average calculator using HashMap

Problem Statement: I have a 2D array of strings containing student names and respective marks as below
String[][] scores = {{"Bob","85"},{"Mark","100"},{"Charles","63"},{"Mark","34"}};
I want to calculate the best average among all the students available, i.e with the above input the best average should be 85.
My Attempt:
I tried to solve this using HashMap as below.
public int bestAverageCalculator(String[][] scores) {
// This HashMap maps student name to their list of scores
Map<String,List<Integer>> scoreMap = new HashMap<String,List<Integer>>();
for(String[] score:scores) {
String name = score[0];
int currentScore =Integer.parseInt(score[1]);
if(scoreMap.containsKey(name)) {
List<Integer> scoreList = scoreMap.get(name);
scoreList.add(currentScore);
scoreMap.put(name, scoreList);
}
else {
List<Integer> scoreList = new ArrayList<Integer>();
scoreList.add(currentScore);
scoreMap.put(name, scoreList);
}
}
//scoreMap will be {Charles=[63], Bob=[85], Mark=[100, 34]}
//After Map is formed i am iterating though all the values and finding the best average as below
int bestAverage = 0;
for(List<Integer> value:scoreMap.values()) {
int sum = 0;
int count = 0;
for(int i:value) {
sum+=i;
count++;
}
int average = (int)Math.floor(sum/count);
if(average>bestAverage)
bestAverage = average;
}
return bestAverage;// returns 85
}
The implementation is correct and i am getting the answer as expected, but i was told the space complexity of the program is more and it can be achieved without using the List<Integer> for marks, i am not able to understand how average can be calculated on fly without storing list of marks.
Please suggest if any other methods can solve this other than HashMap.
Any help would be appreciated.

You could store for each student a constant amount of data :
the student's name
the sum of all the student's marks
the number of the student's marks
This will make the space complexity O(m) where m is the number of unique students (instead of your O(n) where n is the number of marks).
For example, you can have a Student class with these 3 properties (and store the data in a List<Student>), or you can have a Map<String,int[]> with the key being the student's name and the value being an array of two elements containing the sum of the marks and the number of marks.
You can construct this data while iterating over the input.
Now you can compute the average for each student and find the highest average.

Well for space saving you can store two numbers per person
avgSum and count and calculate average on the end.

I have implemented #Eran 's approach based on your code with a Map<String,int[]> with
key: student's name
value: an array of two elements [the sum of the scores, the number of scores]
public int bestAverageCalculator(String[][] scores) {
// This HashMap maps student name to their total scores and count in an int array format of [totalScores, count]
Map<String,int[]> scoreMap = new HashMap<String,int[]>();
for(String[] score:scores) {
String name = score[0];
int currentScore =Integer.parseInt(score[1]);
if(scoreMap.containsKey(name)) {
int[] scoreCount = scoreMap.get(name);
scoreCount[0] += currentScore;
scoreCount[1] ++;
scoreMap.put(name, scoreCount);
}
else {
int[] scoreCount = new int[]{currentScore, 1};
scoreMap.put(name, scoreCount);
}
}
int bestAverage = 0;
for(int[] value:scoreMap.values()) {
int average = (int)Math.floor(value[0]/value[1]);
if(average>bestAverage)
bestAverage = average;
}
return bestAverage;// returns 85
}

#Eran's idea but with Student class, at least for me it's much more clear
import java.util.*;
public class Main {
static String[][] scores = {{"Bob", "85"}, {"Mark", "100"}, {"Charles", "63"}, {"Mark", "34"}};
public static void main(String[] args) {
List<Student> students = new ArrayList<>();
for (String[] score : scores) {
String name = score[0];
int currentScore = Integer.parseInt(score[1]);
Student student = findStudentByName(name, students);
if (student != null) {
student.setNumberOfScores(student.getNumberOfScores() + 1);
student.setSumOfScores(student.getSumOfScores() + currentScore);
} else {
student = new Student(name, 1, currentScore);
students.add(student);
}
}
findStudentWithBestAverage(students);
}
private static void findStudentWithBestAverage(List<Student> students) {
Student bestStudent = null;
int bestAverage = 0;
for (int i = 0; i < students.size(); i++) {
if ((students.get(i).getSumOfScores() / students.get(i).getNumberOfScores()) > bestAverage) {
bestStudent = students.get(i);
bestAverage = (students.get(i).getSumOfScores() / students.get(i).getNumberOfScores());
}
}
System.out.println(bestStudent + " with average: " + bestAverage);
}
private static Student findStudentByName(String name, List<Student> students) {
for (int i = 0; i < students.size(); i++) {
if (students.get(i).getName().equals(name)) {
return students.get(i);
}
}
return null;
}
public static class Student {
private String name;
private int numberOfScores;
private int sumOfScores;
public Student(String name, int numberOfScores, int sumOfScores) {
this.name = name;
this.numberOfScores = numberOfScores;
this.sumOfScores = sumOfScores;
}
public String getName() {
return name;
}
public int getNumberOfScores() {
return numberOfScores;
}
public void setNumberOfScores(int numberOfScores) {
this.numberOfScores = numberOfScores;
}
public int getSumOfScores() {
return sumOfScores;
}
public void setSumOfScores(int sumOfScores) {
this.sumOfScores = sumOfScores;
}
#Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Student student = (Student) o;
return name.equals(student.name);
}
#Override
public int hashCode() {
return Objects.hash(name);
}
#Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", numberOfScores=" + numberOfScores +
", sumOfScores=" + sumOfScores +
'}';
}
}
}

The for loop in the method gets skipped when 3rd entry goes in. JAVA

When I run this code, for some reason when it hits test10 to be added into the Array sort, the addListing method ignores the for loop and just skips to the bottom. I am curious why the for loop runs for test2.addListing(test); and test2.addListing(test9); but not for the one after.
import java.util.Scanner;
public class TestListings {
public static void main(String[] args) {
StudentListings test = new StudentListings();
StudentListings test9 = new StudentListings();
StudentListings test10 = new StudentListings();
test.input();
test9.input();
test10.input();
Scanner sc = new Scanner(System.in);
int aSize = 0;
System.out.print("Enter Array Size: ");
aSize = Integer.parseInt(sc.nextLine());
ArraySort test2 = new ArraySort(aSize);
test2.addListing(test);
test2.addListing(test9);
test2.addListing(test10);
test2.showAllListings();
}
}
This is the method written, and it runs for the first run through, next = 0; intially, but the 3rd time (in test10) it just looks at the line and skips it.
public class ArraySort
{
private StudentListings[] data;
private int size = 0;
private int next = 0;
public ArraySort()
{
data = new StudentListings[size];
size = 0;
next = 0;
}
public ArraySort(int ArraySize)
{
size = ArraySize;
data = new StudentListings[size];
next = 0;
}
public void addListing(StudentListings newListing)
{
System.out.print(next);
for(i = next - 1; i <= 0; i--)
{
try {
if (newListing.compareTo(data[i].getLName()) < 0)
{
data[i+1] = data[i].deepCopy();
}
else
{
data[i+1] = newListing;
next++;
break;
}
}
catch(ArrayIndexOutOfBoundsException | NullPointerException exception)
{
int x = i + 1;
data[x] = newListing;
next++;
break;
}
}
System.out.print(next);
}
public void showAllListings()
{
for(int i = 0; i < next; i++)
{
System.out.println((i + 1) + ". " + data[i]);
}
}
}
This is the class that is getting created to be inserted into the array.
import java.util.Scanner;
public class StudentListings {
private String firstName;
private String lastName;
private int id;
private double gpa;
public StudentListings()
{
firstName = "";
lastName = "";
id = 0;
gpa = 0.0;
}
public StudentListings(String firstName, String lastName, int id,
double gpa)
{
this.firstName = firstName;
this.lastName = lastName;
this.id = id;
this.gpa = gpa;
}
public void setName(String firstName, String lastName)
{
this.firstName = firstName;
this.lastName = lastName;
}
public String getName()
{
return firstName + " " + lastName;
}
public void setId(int id)
{
this.id = id;
}
public int getId()
{
return id;
}
public void setGpa(double gpa)
{
this.gpa = gpa;
}
public double getGpa()
{
return gpa;
}
public String getLName()
{
return lastName;
}
public void input()
{
Scanner sc = new Scanner(System.in);
System.out.print("Enter First Name: ");
this.firstName = sc.nextLine();
System.out.print("Enter Last Name: ");
this.lastName = sc.nextLine();
System.out.print("Enter Student ID: ");
this.id = sc.nextInt();
System.out.print("Enter Student GPA: ");
this.gpa = Double.parseDouble(sc.next());
}
public String toString()
{
return "Last Name: " + lastName + " First Name: " + firstName + " ID:
" + id + " GPA: " + gpa;
}
public StudentListings deepCopy()
{
StudentListings clone = new StudentListings(firstName, lastName, id,
gpa);
return clone;
}
public int compareTo(String targetKey)
{
return(lastName.compareTo(targetKey));
}
}

If next is 0 the first time then it’s 2 the third time and i starts at 1 so the condition i <= 0 is false from the start

I'm not solving that problem, because in my opinion you're trying to do (intricately) something already defined in Java. When you create a class, and have to manage an array of object of that class, Java offers a very simple way to do that, I'll explain what I would do in your position step by step:
1 - The first thing to do is to define the comparison between the object belonging to that class, you can achieve that by overriding the method compareTo of that class (the class has to implement Comparable <YourObject>); in your case i guess it schould be something like:
public class StudentListings implements Comparable<StudentListings>{
...
#Override
public int compareTo(StudentListings element){
return ...;
}
}
In which you define when a StudentListing object is bigger than another.
2 - The second thing to do is to define an ArrayList<StudentListings> in your main, and initialize it:
ArrayList<StudentListings> yourArray = new ArrayList<>();
3 - Then you have to add the elements to that array (obviously after you initialized them):
yourArray.add(test);
yourArray.add(test9);
yourArray.add(test10);
4 - Now you have your array, not sorted, to sort it you just have to call the method
Collections.sort(yourArray);
Now you have your ArrayList of StudentListings sorted.
There is another way to achieve this result, that is described here, I don't like it very much because using that way you have to redefine the comparison everytime you need to sort an array and because your main code results more complex, but it has the same result of the steps I explained (therefore the linked method is useful if you have to sort two different arrays of the same class objects in different ways, eg. one by students name and the other by students surname).

Getting Java methods from one object and a constructor from another object

I have three class Homework that has my main(...), GradeArray, which has my methods, and StudentGrade, which has my constructor.
Currently , which is clearly wrong, I have in Homework:
GradeArray grades = new GradeArray();`
In GradeArray at the top I have StudentGrade[] ArrayGrades = new StudentGrade[size]; however this method did not give me both the contructor and the methods. I know I don't need three classes for this but my professor wants three class. How do I declare an array that has attributes from two classes so that I can get the methods from GradeArray and the constructor from StudentGrade?
Thank you for you time and help.
Here is all of my code
package homework1;
public class Homework1
{
public static int pubSize;
public static String pubCourseID;
public static void makeVarsPub(int maxSize, String courseID) //this is to makes the varibles public
{
pubSize = maxSize;
pubCourseID = courseID;
}
public int giveSize()
{
return pubSize;
}
public static void main(String[] args)
{
int maxSize = 100;
String courseID = "CS116";
//this is to makes the varibles public
makeVarsPub(maxSize, courseID);
StudentGrade grades = new StudentGrade();
grades.insert("Evans", 78, courseID);
grades.insert("Smith", 77, courseID);
grades.insert("Yee", 83, courseID);
grades.insert("Adams", 63, courseID);
grades.insert("Hashimoto", 91, courseID);
grades.insert("Stimson", 89, courseID);
grades.insert("Velasquez", 72, courseID);
grades.insert("Lamarque", 74, courseID);
grades.insert("Vang", 52, courseID);
grades.insert("Creswell", 88, courseID);
// print grade summary: course ID, average, how many A, B, C, D and Fs
System.out.println(grades);
String searchKey = "Stimson"; // search for item
String found = grades.find(searchKey);
if (found != null) {
System.out.print("Found ");
System.out.print(found);
}
else
System.out.println("Can't find " + searchKey);
// Find average and standard deviation
System.out.println("Grade Average: " + grades.avg());
System.out.println("Standard dev; " + grades.std());
// Show student grades sorted by name and sorted by grade
grades.reportGrades(); // sorted by name
grades.reportGradesSorted(); // sorted by grade
System.out.println("Deleting Smith, Yee, and Creswell");
grades.delete("Smith"); // delete 3 items
grades.delete("Yee");
grades.delete("Creswell");
System.out.println(grades); // display the course summary again
}//end of Main
}//end of homework1
package homework1;
class GradeArray
{
int nElems = 0; //keeping track of the number of entires in the array.
Homework1 homework1InfoCall = new Homework1(); //this is so I can get the information I need.
int size = homework1InfoCall.giveSize();
StudentGrade[] ArrayGrades = new StudentGrade[size];
public String ToString(String name, int score, String courseID)
{
String res = "Name: " + name + "\n";
res += "Score: " + score + "\n";
res += "CourseID " + courseID + "\n";
return res;
}
public String getName(int num) //returns name based on array location.
{
return ArrayGrades[num].name;
}
public double getScore(int num) //returns score based on array location.
{
return ArrayGrades[num].score;
}
public void insert(String name, double score, String courseID) //part of the insert method is going to be
//taken from lab one and modified to fit the need.
{
if(nElems == size){
System.out.println("Array is full");
System.out.println("Please delete an Item before trying to add more");
System.out.println("");
}
else{
ArrayGrades[nElems].name = name;
ArrayGrades[nElems].score = score;
ArrayGrades[nElems].courseID = courseID;
nElems++; // increment the number of elements
};
}
public void delete(String name) //code partly taken from lab1
{
int j;
for(j=0; j<nElems; j++) // look for it
if( name == ArrayGrades[j].name)
break;
if(j>nElems) // can't find it
{
System.out.println("Item not found");
}
else // found it
{
for(int k=j; k<nElems; k++) // move higher ones down
{
boolean go = true;
if ((k+2)>size)
go = false;
if(go)
ArrayGrades[k] = ArrayGrades[k+1];
}
nElems--; // decrement size
System.out.println("success");
}
}
public String find (String name){ //code partly taken from lab1
int j;
for(j=0; j<nElems; j++) // for each element,
if(ArrayGrades[j].name == name) // found item?
break; // exit loop before end
if(j == nElems) // gone to end?
return null; // yes, can't find it
else
return ArrayGrades[j].toString();
}
public double avg() //this is to get the average
{
double total = 0;
for(int j=0; j<nElems; j++)
total += ArrayGrades[j].score;
total /= nElems;
return total;
}
public double std() //this is to get the standard deviation. Information on Standard deviation derived from
//https://stackoverflow.com/questions/18390548/how-to-calculate-standard-deviation-using-java
{
double mean = 0; //this is to hold the mean
double newSum = 0;
for(int j=0; j < ArrayGrades.length; j++) //this is to get the mean.
mean =+ ArrayGrades[j].score;
for(int i=0; i < ArrayGrades.length; i++) //this is to get the new sum.
newSum =+ (ArrayGrades[i].score - mean);
mean = newSum/ArrayGrades.length; //this is to get the final answer for the mean.
return mean;
}
public StudentGrade[] reportGrades() //this is grade sorted by name
{
int in,out;
char compair; //this is for compairsons.
StudentGrade temp; //this is to hold the orginal variable.
//for the first letter cycle
for(out=1; out<ArrayGrades.length; out++)
{
temp = ArrayGrades[out];
compair= ArrayGrades[out].name.charAt(0);
in=out;
while(in>0 && ArrayGrades[in-1].name.charAt(0) > compair)
{
ArrayGrades[in] = ArrayGrades[in-1];
in--;
}
ArrayGrades[in]=temp;
}
//this is for the second run.
for(out=1; out<ArrayGrades.length; out++)
{
temp = ArrayGrades[out];
compair= ArrayGrades[out].name.charAt(1);
in=out;
while(in>0 && ArrayGrades[in-1].name.charAt(1) > compair)
{
ArrayGrades[in] = ArrayGrades[in-1];
in--;
}
ArrayGrades[in]=temp;
}
return ArrayGrades;
}
public StudentGrade[] reportGradesSorted() //this is grades sorted by grades.
//this is grabbed from lab2 and repurposed.
{
int in,out;
double temp;
for(out=1; out<ArrayGrades.length; out++)
{
temp=ArrayGrades[out].score;
in=out;
while(in>0 && ArrayGrades[in-1].score>=temp)
{
ArrayGrades[in]= ArrayGrades[in-1];
in--;
}
ArrayGrades[in].score=temp;
}
return ArrayGrades;
} //end of GradeArray
package homework1;
public class StudentGrade extends GradeArray
{
public String name;
double score;
public String courseID;
public void StudentGrade (String name, double score, String courseID) //this is the constructor
{
this.name = name;
this.score = score;
this.courseID = courseID;
}
}//end of StudentGrade class.

First, I feel #Alexandr has the best answer. Talk with your professor.
Your question doesn't make it quite clear what you need. However, it sounds like basic understanding of inheritance and class construction would get you going on the right path. Each of the 3 classes will have a constructor that is unique to that type. Each of the 3 classes will have methods and data (members) unique to those types.
Below is just a quick example of what I threw together. I have strong concerns that my answer is actually what your professor is looking for however--it is not an object model I would suggest--just an example.
public class Homework {
private String student;
public Homework(String name) {
student = name;
}
public String getStudent() {
return student;
}
}
public class StudentGrade extends Homework {
private String grade;
public StudentGrade(String grade, String name) {
super(name);
this.grade = grade;
}
public String getGrade() {
return grade;
}
}
public class HomeworkGrades {
public List<StudentGrade> getGrades() {
// this method isnt implemented but should
// be finished to return array of grades
}
}
Take a look and see if that helps you understand something about inheritance and class construction.
Hopefully you can infer a bit about inheritence (StudentGrade inherits -- in java extends -- from HomeWork) and class construction.
Thnx
Matt

I change the array creation in Homework1 to be StudentGrade grades = new StudentGrade(); and I added extends GradeArray to the StudentGrade class. it is now public class StudentGrade extends GradeArray.

Multiple problems with sort method and toString not working

I'm having an issue with a problem for homework.. the issues I am having are:
I have the following errors on my sort method:
The method sort(int[]) in the type Main is not applicable for the
arguments (Class)
studentArray cannot be resolved to a type
Syntax error, insert ". class" to complete ArgumentList
My toString method also doesnt seem to be putting out any information in the console.
HERE IS THE HOMEWORK PROBLEM:
For the lab this week, you will sort an array of objects - using any of the sort methods discussed in Chapter 23 or the Selection sort. It's your choice. Use the following criteria for your assignment:
The object class should be a Student with the following attributes:
id: integer
name: String
write the accessors, mutators, constructor, and toString().
In your main test class you will write your main method and do the following things:
Create an array of Student objects with at least 5 students in your array.
The sort method must be written yourself and included in the main class. The sort
method will sort based on student id.
Output the array out in unsorted order as it exists.
Sort the array
Output the sorted array
HERE IS MY MAIN CLASS:
public static void main(String[] args) {
Student studentArray[] = new Student[5];
for (int i=0; i < studentArray.length; i++) {
studentArray[i] = new Student();
}
studentArray[0].id = 5555;
studentArray[0].name = "Jim Jackson";
studentArray[1].id = 4444;
studentArray[1].name = "Craig Creedmoor";
studentArray[2].id = 3333;
studentArray[2].name = "Bill Biggums";
studentArray[3].id = 2222;
studentArray[3].name = "Frances Freeland";
studentArray[4].id = 1111;
studentArray[4].name = "Leslie Limerick";
for (int i = 0; i<5; i++) {
studentArray[i].toString();
}
sort(studentArray[]);
for (int i = 0; i<5; i++) {
studentArray[i].toString();
}
}
public void sort(int[] studentArray) {
for (int i = 1; i < studentArray.length; i++) {
int currentElement = studentArray[i];
int k;
for (k = i -1; k >=0 && studentArray[k] > currentElement; k--) {
studentArray[k + 1] = studentArray[k];
}
studentArray[k +1] = currentElement;
}
}
HERE IS MY STUDENT CLASS
public int id;
public String name;
Student() {
}
public int getID() {
return id;
}
public void setID(int i) {
this.id = i;
}
public String getName() {
return name;
}
public void setName(String n) {
this.name = n;
}
public String toString() {
return "The student's name is: " + this.name + "\n" +
"The student's ID is: " + this.id;
}

So according to the assignment instructions, here is what I got from it...
You needed a constructor in your student class, you were adding objects to the array improperly, Your sort method was also accessing the element within the array which is a "Student" and you were comparing it to type "int". To fix that I made the object in the student array actually access the ID.
Also.... Your sort method did not seem to work for me. The instructions said that you could use a selection sort so that is what I implemented instead. Let me know if you have questions.
This should work, let me know if it doesn't because I don't know how your Student class is defined within your project.
public static void main(String[] args) {
Student studentArray[] = new Student[5];
studentArray[0] = new Student(5555, "Jim Jackson");
studentArray[1] = new Student(4444, "Craig Creedmor");
studentArray[2] = new Student(3333, "Bill Biggums");
studentArray[3] = new Student(2222, "Frances Freeland");
studentArray[4] = new Student(1111, "Leslie Limerick");
sort(studentArray);
for (int i = 0; i<5; i++) {
System.out.println(studentArray[i].toString());
}
}
public static void sort(Student[] arr) {
for (int i = 0; i < arr.length - 1; i++)
{
int index = i;
for (int j = i + 1; j < arr.length; j++)
if (arr[j].getID() < arr[index].getID())
index = j;
int smallerNumber = arr[index].getID();
String smallerString = arr[index].getName();
arr[index].setID(arr[i].getID());
arr[index].setName(arr[i].getName());
arr[i].setID(smallerNumber);
arr[i].setName(smallerString);
}
}
And then for Student class
public class Student {
private int id;
private String name;
public Student(int id, String name){
this.id = id;
this.name = name;
}
public int getID() {
return id;
}
public void setID(int i) {
this.id = i;
}
public String getName() {
return this.name;
}
public void setName(String n) {
this.name = n;
}
public String toString() {
return "The student's name is: " + this.name + "\n" +
"The student's ID is: " + this.id;
}
}

Sorting an array of integers in descending order and relating it to its corresponding string array

I am trying to output the names and corresponding scores in descending order. Having an array of strings and another array of integers, I am trying to relate the two arrays. I used Arrays.sort and tries to get the indices. The indices is then to be used to arrange the names in similar location as the corresponding scores. I have this code but I get run time error saying unfortunately, your app has stopped. Can anyone please help me on what to be done to achieve my goal here? Thank you so much!
int score[]= new int[4];
score[0]= 10;
score[1]= 50;
score[2]= 20;
score[3]= 60;
String names[] = new String[4];
names[0]= "player1";
names[1]= "player2";
names[2]= "player3";
names[3]= "player4";
Arrays.sort(score);
int index_array[] = new int[4];
int m = 0;
for(m = 0; m <4; m++){
index_array[m]=Arrays.binarySearch(score ,score[m]);
l = index_array[0];
}
for(int i = 0; i<4; i++){
if(l == score[i]){
j = i;
}
}
String name = names[m];
show.setText(name + " " + Integer.toString(l));

Create Player model which holds player's name and score and then use Comparator to sort players by score.
Player model:
class Player {
private String name;
private int score;
public Player(String name, int score) {
this.name = name;
this.score = score;
}
public String getName() {
return name;
}
public int getScore() {
return score;
}
public String toString() {
return "name=" + name + "; score=" + score;
}
}
Comparator:
class PlayerComparator implements Comparator<Player> {
public int compare(Player p1, Player p2) {
return p1.getScore() < p2.getScore() ? -1
: p1.getScore() > p2.getScore() ? 1 : 0;
}
}
And an example of usage:
public class PlayerTest {
public static void main(String[] args) {
int score[]= new int[4];
score[0]= 10;
score[1]= 50;
score[2]= 20;
score[3]= 60;
String names[] = new String[4];
names[0]= "player1";
names[1]= "player2";
names[2]= "player3";
names[3]= "player4";
Player[] players = new Player[names.length];
for(int i = 0; i < names.length; i++) {
players[i] = new Player(names[i], score[i]);
}
Arrays.sort(players, new PlayerComparator());
}
}

you need to associate the score and the user name. Currently, you are associating them by array index. when you sort the scores, the indices of the scores will change.
Try something like this:
class Score implements Comparable<Score>
{
int score;
String player;
public Score(int theScore, String thePlayer)
{
score = theScore;
player = thePlayer;
}
public int compareTo(Score)
{
... compare based on the int score value ...
}
... getters. setters optional ...
}
List<Score> scoreList = new ArrayList<Score>();
... fill scoreList with Score objects. ...
Collections.sort(scoreList);

This is a design smell. You shouldn't have two parallel arrays. Instead, you should have a single array of Player objects, where each Player would have a name and a score.
Storing the arra of players by name or by score would then be extremely simple.
Java is an OO language. Use objects.
public class Player
private final String name;
private int score;
public Player(String name, int score) {
this.name = name;
this.score = score;
}
public String getName() {
return name;
}
public int getScore() {
return score;
}
public void setScore(int score) {
this.score = score;
}
}
...
Player[] players = new Player[4];
players[0] = new Player("player1", 10);
...