Cash Register Program (processing "sales" and "amounts" )

Question

I'm having trouble adding amounts to an array of capacity that the user sets at the beginning of the program. It seems very easy, but I just don't know what to do. It is for a school assignment, so I'm not asking for any freebies. I'd just like to be pointed in the right direction with hints or any useful info. A skeleton was included with the assignment which makes me feel less capable because it's all broken down. Some methods were included. The CashRegister class contains all the methods of the cash register (add amount, remove first occurrence of amount, remove all occurrences, etc.) I'm only lacking the add amount, and both remove occurrence methods.
I think i wrote the add amount method somewhat correctly.. although I'm unsure of how to implement it in case 2 of the switch obviously not as simple as addAmount();
// CashRegister.java
   import java.text.NumberFormat;
   import java.util.Scanner;
    public class CashRegister
      Scanner scan = new Scanner (System.in);
        //instance variables
      private double[] amounts;
      private int numOfValues;
        //constructor
       public CashRegister( int size )
         amounts = new double[ size ];
         numOfValues = 0;
        //increase size of array when needed
       private void increaseSize ()
         double[] temp = new double[amounts.length + 4];
         for (int count=0; count<amounts.length; count++)
            temp[count] = amounts[count];
         amounts = temp;                    
        //add amount to array
       private void addAmount(double newAmt)
         if (numOfValues == amounts.length)
            increaseSize();
         System.out.print ("Enter amount to be added: ");
         newAmt = scan.nextDouble();
         amounts[numOfValues] = newAmt;
         numOfValues++;     
        //toString method
        //returns String representation of CashRegister object
       public String toString()
           //to be used in formating currency values
         NumberFormat fmt = NumberFormat.getCurrencyInstance();
           //initialize resulting String
         String result = "\n";
           //Check if array is empty.
           //If so, print accordingly.
         if( numOfValues == 0 )
            result += "There are 0 register amounts at this time.\n";
         //otherwise, place amounts in result String
         else
         //build result String with amounts
            for( int i = 0; i < amounts.length; i++ )
               result += ( i + 1 ) + ": " + fmt.format( amounts[ i ] ) + "\n";
           //return result String
         return result;
// Project7ADriver.java
   import java.util.Scanner;
    public class Project7ADriver
       public static void main( String[] args )
           //Start Scanner to take input
         Scanner scan = new Scanner( System.in );
           //instantiate a CashRegister
         System.out.print( "How many amounts would you like your register to hold? " );
         int numElements = scan.nextInt();
         CashRegister cr = new CashRegister( numElements );
         int userChoice = 0;
         while( userChoice != 5 )
            menu();
            userChoice = scan.nextInt();
            menuSwitch( userChoice, cr );
       public static void menuSwitch( int choice, CashRegister cashReg )
           //Start Scanner to take input
         Scanner scan = new Scanner( System.in );
         switch( choice )
           //print out amounts
            case 1:
               System.out.print( cashReg.toString() );
               break;
            case 2:
            case 5:
               System.out.println("\nGoodbye!");
               break;
            default:
               System.out.println("Sorry, invalid choice");
       public static void menu()
         System.out.println("\nCash Register");
         System.out.println("*************");
         System.out.println("1: Print the sale amounts");
         System.out.println("2: Add amount");
         System.out.println("3: Remove first occurrence of an amount");
         System.out.println("4: Remove all occurrences of an amount");           
         System.out.println("5: Quit");
         System.out.print("\nEnter your choice: ");
   }

Answer 1

looks like your method signature is wrong
private void addAmount(double newAmt)the method itself gets the amount
newAmt = scan.nextDouble();so its a bit hard passing the amount, when you first call the method
try it like this
      private void addAmount()
         if (numOfValues == amounts.length)
            increaseSize();
         System.out.print ("Enter amount to be added: ");
         double newAmt = scan.nextDouble();
         amounts[numOfValues] = newAmt;
         numOfValues++;     
      }and in your switch
case 2:
  addAmount();
  break;