将文件读入多个对象的arraylist java

Question

So this is my main class, am basically trying to read from a txt file a list of items and am trying to store them in an arraylist of multiple objects but for some reason I keep getting an inputmissmatch error if I tried to have multiple lines in the txt file and multiple objects, however let's say I have a txt that has one line & I add one object to the list, it works perfectly fine

public static void main(String[] args) throws FileNotFoundException, IOException {
        
                //    FileReader fr = new FileReader("Item2.txt");
                Scanner file = new Scanner(new File("item.txt"));
                ArrayList<Item> List = new ArrayList<Item>();
             
                   List.add(new ClothingItem(file.next().charAt(0), file.next(), file.next(), file.nextInt(), file.next(), file.nextDouble(), file.nextInt()));
                    List.add(new ClothingItem(file.next().charAt(0), file.next(), file.next(), file.nextInt(), file.next(), file.nextDouble(), file.nextInt()));
                    List.add(new Computer(file.nextInt(), file.next(), file.nextDouble(), file.nextInt(), file.next(), file.next(), file.next(), file.nextDouble(), file.nextDouble()));
                    List.add(new FoodItem(file.nextDouble(), file.next(), file.nextInt(), file.next(), file.nextDouble(), file.nextInt()));
                    List.add(new FoodItem(file.nextDouble(), file.next(), file.nextInt(), file.next(), file.nextDouble(), file.nextInt()));
                    List.add(new Beverages(file.nextInt(), file.next(), file.nextInt(), file.next(), file.nextDouble(), file.nextInt()));
           
        
                ClothingItem[] list1 = List.toArray(new ClothingItem[List.size()]);
                ClothingItem[] list2 = List.toArray(new ClothingItem[List.size()]);
                Computer[] list3 = List.toArray(new Computer[List.size()]);
                FoodItem[] list4 = List.toArray(new FoodItem[List.size()]);
                FoodItem[] list5 = List.toArray(new FoodItem[List.size()]);
                Beverages[] list6 = List.toArray(new Beverages[List.size()]);
        
                for (Item A : List) {
                    System.out.println(A);
         }
                
            }
        }  

File that am trying to read

M RED MALE 1001 Shirt 19.0 100
L BLACK FEMALE 1002 Shoes 49.0 25   
1003 Thinkpad 1050.0 2 Samsung i710610U SMEF 8.0 512.0
5.0 NotFresh 1004 GreenPeas 3.0 117 
5.0 Fresh 1005 Lettuce 2.0 90 
1006 NotAlcholic 1981 Cola 3.0 50  

Answer 1

This error occur when you use

file.nextInt() or file.nextDouble()

on a next value which is not an integer nor double. In the lines of your code a string ends up with nextInt() or nextDouble() which causes the error.

You made 2 mistakes.

1)The first mistake is that you have 1 line that does not correspond to your data.

        List.add(new Computer(file.nextInt(), file.next(), file.nextDouble(), file.nextInt(), file.next(), file.next(), file.next(), file.nextDouble(), file.nextDouble()));

This is the fourth line in your loop. This line causes conflictions as it was design to run with the third line from your text file, but at this line of code we using it on the fourth line from your text file. Just comment it out or remove it.

2)The last mistake is in the last 3 lines of your code. You use the the method: file.hasNext()

hasNext returns a boolean which tells us whether there is more data after our current position, but it does not go to the next value. The cause of this mistake is for example when we call next() again we should get a string, but you called hasNext(), it does not move to the next value. So when you call nextInt we get a string as our next() value is a string.

change hasNext() to next()

Also there is no need for a while loop if you reference every value manually.

Also your while loop that prints the item values is just gonna print the object string which isn't helpful.