El método de clasificación produce un error de modificación concurrente cuando uso temp = iterator.next (). ¿Me pueden ayudar, por favor, a resolver el error de modificación concurrente? Di el código para toda la clase, pero solo estoy intentando completar el método de clasificación. Gracias de antemano por tu ayuda.

Tengo que ordenar todos los arreglos en el arrailista.

    package HashSet;

            import java.io.InputStream;
            import java.util.ArrayList;
            import java.util.Collections;
            import java.util.ListIterator;
        import java.util.Scanner;

        public class PhoneBook {
            int capacity = 10;
            private ArrayList<PhoneBookEntry>[] buckets;

            public PhoneBook() {
                this(10);
                load();
            }

            public PhoneBook(int size) {
                capacity = size;
                buckets = new ArrayList[size];
                for (int i = 0; i < buckets.length; i++)
                    buckets[i] = new ArrayList<PhoneBookEntry>();
            }

            public int getSize() {
                int tot = 0;
                for (ArrayList<PhoneBookEntry> x : buckets)
                    tot += x.size();
                return tot;
            }

            public boolean add(PhoneBookEntry entry) {
                if (contains(entry))
                    return false;
                int x = Math.abs(entry.hashCode());
                buckets[x % buckets.length].add(entry);
                return true;
            }

            public void load() {
                InputStream is = getClass().getClassLoader().getResourceAsStream(
                        "phone.txt");
                Scanner scan = new Scanner(is);
                while (scan.hasNext())
                    add(new PhoneBookEntry(scan.next(), scan.nextInt()));
                scan.close();
            }

            public void bucketSize() {
                for (int i = 0; i < buckets.length; i++)
                    System.out.println(i + "    " + buckets[i].size());
            }

            public boolean contains(PhoneBookEntry word) {
                int x = Math.abs(word.hashCode());
                return buckets[x % buckets.length].contains(word);
            }

            public int getCapacity() {
                return capacity;
            }

            public int getLongestList() {
                int numb = 0;
                for (ArrayList<PhoneBookEntry> x : buckets)
                    if (x.size() > numb)
                        numb = x.size();
                return numb;
            }

            public void display() {
                for (ArrayList<PhoneBookEntry> x : buckets)
                    System.out.println(x);
            }

            public int getNumberOfNulls() {
                int numb = 0;
                for (ArrayList<PhoneBookEntry> x : buckets)
                    if (x.size() == 0)
                        numb++;
                return numb;
            }

            public String lookup(String name) {
                String numb = name + "'s number not found";
                for (ArrayList<PhoneBookEntry> x : buckets)
                    for (int i = 0; i < x.size(); i++)
                        if (x.get(i).getN().equals(name))
                            numb = name + "'s" + " number is " + x.get(i).getNr();
                return numb;
            }

            public int internalLookUp(String name) {
                int numb = 0;
                for (ArrayList<PhoneBookEntry> x : buckets)
                    for (int i = 0; i < x.size(); i++)
                        if (x.get(i).getN().equals(name))
                            numb = x.get(i).getNr();
                return numb;
            }

            public void sort() {
                String temp = "";
                ArrayList<String> list = new ArrayList<String>();
                ListIterator<String> iterator = list.listIterator();
                final ArrayList<PhoneBookEntry>[] data = buckets.clone();
                for (ArrayList<PhoneBookEntry> x : buckets) {
                    for (int i = 0; i < x.size(); i++) {
                        list.add(x.get(i).getN());
                    }
                    Collections.sort(list);
                    for (int b = 0; b < x.size(); b++) {
                        temp = iterator.next(); //error line
                        x.get(b).setN(temp);
                        x.get(b).setNr(internalLookUp(temp));
                    }
                }
            }

            public static void main(String[] args) {
                PhoneBook phone = new PhoneBook();
                phone.display();
                System.out.println();
                System.out.println("Capacity is " + phone.getCapacity());
                System.out.println();
                System.out.println("Size is " + phone.getSize());
                System.out.println();
                System.out.println("Get longest list " + phone.getLongestList());
                System.out.println();
                System.out.println("Number of Nulls " + phone.getNumberOfNulls());
                System.out.println();
                System.out.println(phone.lookup("Fish"));
                phone.sort();
            }
        }