java - I'm almost finished, but how to loop the entire program? -

my cash register program complete, can process sales , returns , adds or subtracts money in register.

my problem once i'm done adding values example, program closes , cant figure out how loop choice menu. tried using loop , while loop yelled @ me saying had invalid input (probably because have press f stop when you're checking out).

how can loop whole thing?

import java.util.scanner; import java.util.arraylist;   public class assignment3_000848913 {     public static void main(string[] args)     {         scanner in = new scanner(system.in);         arraylist<integer> prices = new arraylist<integer>();         arraylist<integer> returnprices = new arraylist<integer>();         int totalregistermoney = 0;         int choice = 0;          system.out.print("what do?");         system.out.println();         system.out.print("press 1. process sale");         system.out.println();         system.out.print("press 2. process return");         system.out.println();         system.out.print("press 3. display money in register");         system.out.println();         system.out.print("press 4. exit");         system.out.println();         choice = in.nextint();           if(choice == 1)         {             //this loop reads in prices//             system.out.print("press f when finished.");             system.out.println();                         {                 system.out.print("enter integer price of item: $");                 int = in.nextint();                 prices.add(i);                 system.out.println();             }             while(in.hasnextint());               int totalprice = processsale(prices);             totalregistermoney = totalregistermoney + totalprice;             system.out.print("your total comes $");             system.out.println(totalprice);         }         if(choice == 2)         {             system.out.print("press f when finished.");             system.out.println();                         {                 system.out.print("enter price of returned item: $");                 int j = in.nextint();                 returnprices.add(j);                 system.out.println();             }             while(in.hasnextint());               int returntotal = processreturn(returnprices);             if(returntotal > totalregistermoney)             {                 system.out.print("sorry, there's not money in register.");                 system.out.println();             }             else             {                 totalregistermoney = totalregistermoney - returntotal;             }              system.out.print("you've completed return.");             system.out.println();         }         if(choice == 3)         {             viewbalance(totalregistermoney);         }       }       //end of main  

if getting error when did do..while, doing ok.

the problem after writing 'f' exit option 1 , loop returns , tries convert 'f'

choice = in.nextint(); 

this causes error bucause 'f' not number. need put

in.next(); 

after

while(in.hasnextint()); 

this happen on option 2 in code