private void incrementUse()
  {
    useCount = useCount + 1; 
  }

main() Can't use a Private Method

Here is a main() that mistakenly tries to change useCount:

class CheckingAccount
{
  private String accountNumber;
  private String accountHolder;
  private int    balance;
  private int    useCount = 0;
  . . . .

  private void incrementUse()
  . . . .
}

class CheckingAccountTester
{
  public static void main( String[] args )
  {
    CheckingAccount bobsAccount = new CheckingAccount( "999", "Bob", 100 );

    bobsAccount.processCheck( 50 );
    bobsAccount.incrementUse();
    bobsAccount.useCount = 15;
  }
}