plz help.i can't understand this question

package com.codegym.task.task17.task1713;

import java.util.*;

/*
Shared list

*/

public class Solution implements List<Long>{
    private ArrayList<Long> original = new ArrayList<>();

    public static void main(String[] args) {

    }
    public synchronized ArrayList<Long>  subList(int a,int b){

    }
    public synchronized ListIterator listIterator(){

    }
     public synchronized ListIterator listIterator(int i){

    }