Thread: Count number of 'coin'p coins in a "machine"

[SOLVED]

Hello for my recent assignment I've been tasked to create a ticket machine which accepts payments in and allows you to cancel them. A recent extension to the assignment was to count how many of the pennies being added were a certain type of penny, e.g 10p, 20p, 50p.

I managed to get the program to accurately count the number of 10p within the machine but when I tried with 20's I came to a dead end.

Heres the code that calculates how many 10/20/50ps are in the machine:

class ProcessMoney
{
int ticket;
int cost = 0;
int machine;
int pence = 0;
int calc = 0;
 
public void setTicketPrice( int amount ) {
 
   ticket = amount;
 
}
 
public int getTicketPrice() { 
 
   return ticket;
 
    }
 
 
public void add( int coin ) {
 
    cost = cost + coin;
 
    if ( coin == 10 ){
        calc = calc + 1;
    }
 
 
    } 
 
public boolean enough() { return true; }
 
public int getPaidSoFar() { return cost; }
 
  public void cancel() {
 
      cost = 0;
 
} 
 
public void bought() {
 
      machine = machine + cost;
      cost = 0;
 
    }
 
  public int moneyInMachine() { 
 
      return machine;
 
}
 
public int getCoins( int coin ) {
 
     if ( coin == 10 ){
     pence = machine * 100;
     calc = pence / 1000;
     }
     else if ( coin == 20 ){
         pence = machine * 100;
         calc = pence / 2000;
        }
 
     return calc;
    }
}

Heres the code for testing it:

class Main
{ 
  private static ProcessMoney pm = new ProcessMoney();
 
  public static void main( String args[] )
  {
    int res = 0, expected = 100;
 
    test( "setTicketPrice() & getTicketPrice() ");
 
    pm.setTicketPrice( expected );
    res = pm.getTicketPrice();
    check( res == expected, 
          "Ticket price is %d should be %d", res, expected );
 
    expected = 200;
    pm.setTicketPrice( expected );
    res = pm.getTicketPrice();
    check( res == expected, 
          "Ticket price is %d should be %d", res, expected );
 
    test( "add() & getPaidSoFar()");
 
    pm.add( 10 ); pm.add( 20 ); pm.add( 30 );
    expected = 60;
    res = pm.getPaidSoFar();
    check( res == expected, 
          "Money entered into machine is %d should be %d", res, expected );
    pm.add( 20 ); pm.add( 40 ); pm.add( 40 );
    expected = 160;
    res = pm.getPaidSoFar();
    check( res == expected, 
          "Money entered into machine is %d should be %d", res, expected );
 
    test( "add() & cancel()");
 
    pm.add( 10 ); pm.add( 20 ); pm.add( 30 );
    expected = 0;
    pm.cancel();
    res = pm.getPaidSoFar();
    check( res == expected, 
          "money entered into machine is now %d should be 0", res );
 
    pm.add( 100 ); pm.add( 200 ); pm.add( 300 );
    expected = 0;
    pm.cancel();
    res = pm.getPaidSoFar();
    check( res == expected, 
          "money entered into machine is now %d should be 0", res );
 
    test( "enough()");
 
    pm.setTicketPrice( 200 );
    pm.add( 100 ); pm.add( 100 ); pm.add( 0 );
    expected = 200;
    check( pm.enough(), 
          "Enough money entered into machine 200 for 200 ticket" );
    pm.cancel();
 
    pm.setTicketPrice( 210 );
    pm.add( 100 ); pm.add( 100 ); pm.add( 20 );
    expected = 200;
    check( pm.enough(), 
          "Enough money entered into machine 220 for 210 ticket" );
    pm.cancel();
 
    test( "bought() & moneyInMachine()");
 
    pm.setTicketPrice( 200 );
    pm.add( 100 ); pm.add( 100 ); pm.add( 0 );
    if ( pm.enough() )
    {
      pm.bought();
    }
 
    expected = 200;
    res = pm.moneyInMachine();
    check( expected == res,
          "Total money in machine %d should be %d", res, expected );
    res = pm.getPaidSoFar();
    check( res == 0, 
          "Money for ticket in machine is %d should be 0", res );
    pm.cancel();
 
 
    pm.setTicketPrice( 200 );
    pm.add( 100 ); pm.add( 100 ); pm.add( 10 );
    if ( pm.enough() )
    {
      pm.bought();
    }
 
    expected = 410;
    res = pm.moneyInMachine();
    check( expected == res,
          "Total money in machine %d should be %d", res, expected );
    res = pm.getPaidSoFar();
    check( res == 0, 
          "Money for ticket in machine is %d should be 0", res );
 
    test("Count coins");
    pm = new ProcessMoney();
    checkRecord( 10, 2 );
    checkRecord( 20, 4 );
    checkRecord( 50, 3 );
    checkRecord( 100, 3 );
    checkRecord( 200, 2 );
 
    System.out.println( "Success" );
  }
 
  private static void checkRecord( int coin, int howMany )
  {
     pm.setTicketPrice( howMany * coin );
 
     for ( int i=1; i<=howMany*2; i++ )
     {
       pm.add( coin );
     }
     pm.cancel();
 
     for ( int i=1; i<=howMany; i++ )
     {
       pm.add( coin );
     }
 
     pm.bought();
     int actual = pm.getCoins( coin );
     check( howMany == actual,
            "Expected %d - %dp coins found %d - %dp coins", 
             howMany, coin, actual, coin  );
  }
 
  private static String what = "";
 
  public static void check( boolean ok, String fmt, Object... params )
  {
    if ( ! ok )
    {
      System.out.println( what );
      System.out.print("ERROR: " );
      System.out.printf( fmt, params );
      System.out.println();
      System.exit(-1);
    }
  }
 
  public static void test( String str )
  {
    what = "Test: "  + str;
  }
 
}

For example when I run the program at the moment it runs perfectly for the 10ps however when I run it for 20ps I get these results back:

Test: Count coins
ERROR: Expected 4 - 20p coins found 5 - 20p coins