error when adding to Jlist from arrayList

Question

I am trying to make a program that takes the number of students that are going to be graded and then get the x number of grades and bubble sort them in ascending order.

I am not sure how to add the grades from the arraylist to jlist and output it. this is my error:

Unresolved compilation problem: 
    The method setListData(Integer[]) in the type JList<Integer> is not applicable for the arguments (Object[])

This is my code:

import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import javax.swing.JList;

public class bubbleSwing {

    private JFrame frame;
    private JTextField inputNoOfGrades;
    private JTextField inputGrades;
    private String inputStr;
    private JLabel tvNoOfGrades;
    private JButton btnNoOfGrades;
    private JLabel tvGrades;
    private JButton btnGrades;
    private JButton btnSort;
    private JList<Integer> list;

    ArrayList<Integer> grades = new ArrayList<Integer>();



    private int numOfGrades;
    private int inputGradesInt;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    bubbleSwing bubbleSwing = new bubbleSwing();
                    bubbleSwing.frame.setVisible(true);

                } catch (Exception e) {
                    e.printStackTrace();
                }

            }
        });

    }

    /**
     * Create the application.
     */
    public bubbleSwing() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setBounds(100, 100, 450, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);

        tvNoOfGrades = new JLabel("New label");
        tvNoOfGrades.setBounds(10, 11, 150, 29);
        frame.getContentPane().add(tvNoOfGrades);

        tvGrades = new JLabel("New label");
        tvGrades.setBounds(170, 11, 150, 29);
        frame.getContentPane().add(tvGrades);

        inputNoOfGrades = new JTextField();
        inputNoOfGrades.setBounds(10, 51, 86, 20);
        frame.getContentPane().add(inputNoOfGrades);
        inputNoOfGrades.setColumns(10);

        inputGrades = new JTextField();
        inputGrades.setBounds(158, 51, 86, 20);
        frame.getContentPane().add(inputGrades);
        inputGrades.setColumns(10);

        btnNoOfGrades = new JButton("Submit");
        btnNoOfGrades.setBounds(10, 82, 89, 23);
        frame.getContentPane().add(btnNoOfGrades);

        btnGrades = new JButton("Submit grades");
        btnGrades.setBounds(156, 83, 101, 20);
        frame.getContentPane().add(btnGrades);

        btnSort = new JButton("Sort");
        btnSort.setBounds(290, 61, 89, 23);
        frame.getContentPane().add(btnSort);

        list = new JList<Integer>();
        list.setBounds(60, 116, 167, 135);
        frame.getContentPane().add(list);
        btnNoOfGrades.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                getNoOfGrades();

            }
        });
        btnGrades.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                addToList();

            }
        });

        btnSort.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                bubbleSort(grades);

            }
        });
    }

    private void addToList() {
        inputStr = inputGrades.getText().toString().replaceAll(" ", "");

        if (inputStr.isEmpty()) {
            tvGrades.setText("no grades added");
        } else {
            // converts string to integer and checks if item is already
            // added

            if (grades.size() < numOfGrades) {

                inputGradesInt = Integer.parseInt(inputStr);
                if (inputGradesInt < 0 || inputGradesInt > 10) {

                    tvGrades.setText("Enter a grade between 1-10");
                } else {

                    grades.add(inputGradesInt);
                    list.setListData( grades.toArray()); 

                    inputGrades.setText("");
                    list.notify();
                }

            } else {

                btnSort.setEnabled(true);
            }

        }

    }

    private void getNoOfGrades() {

        inputStr = inputNoOfGrades.getText().toString();//.replaceAll(" ", "");

        if (inputStr.isEmpty()) {
            tvNoOfGrades.setText("no items added");
        } else {
            // converts string to integer and checks if item is already
            // added

            numOfGrades = Integer.parseInt(inputStr);
            if (numOfGrades > 0) {
                inputNoOfGrades.setEnabled(false);
                btnNoOfGrades.setEnabled(false);
                tvGrades.setText("Enter " + numOfGrades
                        + " student grades between 1-10");
            }
        }

    }

    private void bubbleSort(ArrayList<Integer> grades) {

        for (int i = grades.size() - 1; i >= 0; i--) {
            for (int j = 0; j < i; j++) {
                if (grades.get(j) > grades.get(j + 1)) {
                    int temp = grades.get(j);
                    grades.set(j, grades.get(j + 1));
                    grades.set(j + 1, temp);
                }
            }
        }
    }

}

Answer 1

Collection.toArray() returns Object[]. You need to use Collection.toArray(T[]) to get an array of your specific object type:

list.setListData(grades.toArray(new Integer[grades.size()]));