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ArrayList help

843785 Newbie
Currently Being Moderated
Hi, I need to make a class for homework that uses ArrayLists but I am stuck on a method where we have to reverse all the items inside. The program will compile but whenever I run it the program has an error can anyone help?
import java.util.*;

public class Purse
{
     ArrayList<String> purse;
     
     public Purse()
     {
          purse = new ArrayList<String>();
     
     }
     
     public void addCoin(String coinName)
     {
          purse.add(coinName);
     }
     
     public String toString()
     {     
          String out = "]";
          String space = ",";
          String start = "Purse[";
          
          System.out.print(start);
          
          for(int i = 0;i < purse.size(); i++)
          {
               System.out.print(purse.get(i));
               if(i!=purse.size()-1)
                    System.out.print(space);
          }
          
          System.out.print(out);
          System.out.println();
          System.out.println("The array size is: " + purse.size());
          return out;
     }     
     
     public void reverse()
     {
          int a = purse.size();
          for(int i = 0; i < a; i++)
          {
               String temp = purse.get(i);
               purse.set(i, purse.get(a));
               purse.set(a, temp);
               a--;
          }
     }
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