something I don't even know

Test.java

import java.util.ArrayList;
import javax.swing.*;


public class Test{

enum concentrations {MATH, SCIENCE, ENGLISH, WEB};

    public static void main(String[] args) {
        ArrayList<String> names = new ArrayList<String>();   //stores  student's names
        int[] stuConc = new int[500];   //stores student's concentration pick
        int[] concentCount = new int[4];

        input(names, stuConc);
        count(stuConc, concentCount);
        output(names, concentCount, concentrations);

    }

    private static void input(String[] stuNames, int[] stuPick)
    {
        int i = 0;
        do
        {
            stuNames[i] = JOptionPane.showInputDialog("Student's name: ");
            stuPick[i] = Integer.parseInt(JOptionPane.showInputDialog("Your concentration: \n1. DTP\n2. INFS\n3. NTEL\n4. WDM"));
            i++;
        }
        while(JOptionPane.showConfirmDialog(null, "Another student?")==JOptionPane.YES_OPTION);
    }



private static void output(ArrayList<String> names, int[] concentCount, String[] concent)
    {
        ArrayList<String> nameList= new ArrayList<String>();
        ArrayList<String> concentCountList = new ArrayList<String>();

        for(int i =0; i < names.length; i++)
        {
            nameList.add(names[i]);

        }

        for(int i=0; i<concent.length; i++)
        {
            concentCountList.add(concent[i]+ ": "+ concentCount[i]);
        }

        JOptionPane.showMessageDialog(null, nameList);


    }
}