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  1. #1
    reader34 is offline Member
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    Default Close but help would be grateful

    Hey guys i am learning java at college and i have a task to do.. basically my task is to create a airline booking system, this consists of:

    Please select from the following options:

    1- Book a luxury seat.
    2 Book an executive seat.
    3- Display seats/availability
    4- Exit

    Now the code can book a luxury seat ( though i have only created one for the timebeing). When I enter in two types of information from two different customers, I press option 2 and it asks for name( I want the name to find the name that was entered before binded to that seat) It will throw a wobbley saying " NullpointerException:null" at the if (tks [ count] = 0; count < ticketTot; count ++. I think i know why this is happening because its trying to show a int but its a String and its that what I want to show a String, is there anyway of getting around this problem?
    Reader34

    Java Code:
    import java.util.Scanner;
    class Libary 
    {
            static final  int quit = 0;
            
                public static int getMenuOpt()
                {
                     
                    
                    Scanner menuOpt = new Scanner (System.in);
                    int option;
                    
                    System.out.println("Welcome to CCN jet");
                    System.out.println("Please select a option below.");
                   
                       System.out.println("------------------------------");
                        System.out.println("1.Book a luxury seat");
           
                       System.out.println("2. list bookings ");
              
                     
                                System.out.println(quit + ".Quit");
                                
                                option  = menuOpt.nextInt();
                                return option;
                                
                            }
                            
                            public static int addTicket (Ticket tks [], int ticketTot)
                            {
                                Scanner input = new Scanner (System.in);
                                String name;
                                String seatClass;
                       
                  
                          
                                
                              
                               System.out.println("You have chosen to luxury");
                    
                            
                                   
                                System.out.print ("Enter your name ");
                                name = input.nextLine();
                                System.out.print("Please comfirm booking type , Enter Luxury");
                                seatClass = input.nextLine();
                            
                               
                                
                                System.out.println("thank you your details are :"+ name + seatClass );
                                tks [ticketTot] = new Ticket( name, seatClass);
                                ticketTot++;
                                return ticketTot;      
                                
                               
                                
                                
    
                                
                   
                                
                            }
                               
                            public static void listByName (Ticket tks [], int ticketTot)
                            {
                                
                                
                                Scanner input = new Scanner (System.in);
                              
                                String name;
                                String seatClass;
                                System.out.print("Enter your name");
                                name = input.next();
                                
                                for  ( int count = 0 ; count < ticketTot;  count ++ )
                                {
    
                                    System.out.println( tks [count].getName ());
                                    System.out.println(tks [count].getSeatClass ());
                                    
                                       
                                        
    
                                                
                                          
                                        }
                               
             
                                }
                                public static void main (String [] args)
                                {
                                   
                                   Scanner input = new Scanner (System.in);
                                    
    
                               
                                    Ticket tickets [] = new Ticket [5]; 
                                
                            
                                    int ticketsInLibrary = 1;
                                    int option;
                                    int seatsInLibrary=1;
                                  
                                    
                                    
                                    
                                    option = getMenuOpt();
                                    
                                   
                     
                                    
                                    while (option != quit)
                                    {
                                        if (option == 1)
                                            ticketsInLibrary = addTicket (tickets, ticketsInLibrary );
                                            
                                            
                                  
                                            
                                          if (option == 2 )
                                           
                                            
                                            listByName ( tickets, seatsInLibrary);
                                                System.out.println(" Seat number " + seatsInLibrary++  );
                                          
                                                
                                          
                                                    
                                           
                           
                                             
                                                
                                                option = getMenuOpt();
                                            }
    
                                        }
    
                                    }
    
    
                                        
                                               
                                    
                                    
                                    
                                
                                
                                
    import java.util.Scanner;
    
    class Ticket
    {
            
        
                private String name;
                private String seatClass;
    
                
               
           
                
            
                
                Ticket ( String  n, String s)
                {
                    
                    name = n;
                    seatClass = s;
    
                  
                    
                 
    
                }
                
                            
                    String getName ()
                    {
                        return name;
                        
                    }
                    
                    String  getSeatClass()
                    
                    { return seatClass;
                        
                    }
                    
                  
                    }

  2. #2
    Eranga's Avatar
    Eranga is offline Moderator
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    Default

    Can you bit clear it up?

    Do you want to convert a string into an int to fix this problem? How can NullPointerException solve by that? It's better if you can copy-paste here full error message and the inputs you used.

  3. #3
    mtyoung is offline Senior Member
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    Default

    Array index start from 0, not 1....
    how can you add ticket to index 1 and remain index 0 as null?

  4. #4
    Eranga's Avatar
    Eranga is offline Moderator
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  5. #5
    mtyoung is offline Senior Member
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    Default

    Practice only

  6. #6
    Eranga's Avatar
    Eranga is offline Moderator
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  7. #7
    reader34 is offline Member
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    Default

    Ahhh thanks i changed both my values in the array from = 1 to = 0 and now when i enter in a name of someone who has booked a ticket there name type and seat number comes up. I have one question if anybody doesn't mind helping? I want to show a user how many seats are left and taken, would i use some sort of loop to do this? like count every seat and then show whats left.
    thanks
    reader34

  8. #8
    Eranga's Avatar
    Eranga is offline Moderator
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  9. #9
    CJSLMAN's Avatar
    CJSLMAN is offline Moderator
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    Default Arrays?

    You can use an array to keep track of the seats. Since you're using arrays in your code, I'll assume you know the basics and don't need a tutorial, but here's the Array API so you can see all the methods that can be used:
    Array (Java Platform SE 6)
    Luck,
    CJSL
    Chris S.
    Difficult? This is Mission Impossible, not Mission Difficult. Difficult should be easy.

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