Is there any ways to save external file “information” into array in java?

问题

e.g: (I took the first line of the external file)

Giant, Colgate Toothpaste, 4.50

I want to separate & save them in an array like this before/after I send them to the object & ArrayList.

mall[i] = "Giant";
product[i] = "Colgate Toothpaste";
price[i] = 4.50

p/s: I think I should do that because I need to alter the price in the future.

This is how my coding looks like right now.

public static void readFile(ArrayList<Product> productList) throws Exception {
        try {
            productList.clear(); //clear the list! or remove all elements from the list!
            // Coding Here
        }
        catch(Exception e) { System.err.println(e.getMessage());}
    }

Below is the content of the "product.in" file (external file)

Giant, Colgate Toothpaste, 4.50
Giant, Dashing Deodorant, 6.55
Giant, Adidas Deodorant, 7.55
Giant, Dettol Hand-sanitiser, 10.00
Giant, Sokubutso Shower Foam, 15.00
Tesco, Colgate Toothpaste, 4.55
Tesco, Dettol Hand-sanitiser, 7.00
Tesco, Sokubutso Shower Foam, 15.05
Tesco, Adidas Deodorant, 7.45
Tesco, Dashing Deodorant, 5.45
TF, Sokubutso Shower Foam, 15.05
TF, Dettol Hand-sanitiser, 9.50
TF, Adidas Deodorant, 8.55
TF, Dashing Deodorant, 7.55
TF, Colgate Toothpaste, 5.00

If you think I provide you less information, just reply to this thread about it. I'll provide more.

edited: add product class

class Product {
    private String store;
    private String item;
    private double price;

    public Product(String store, String item, double price) {
        this.setStore(store);
        this.setItem(item);
        this.setPrice(price);
    }

回答1:

Plain implementation without extra libraries like OpenCSV or similar would be

Read the file line by line using BufferedReader and try-with-resources to make sure the file resource is closed automatically upon processing.
Split each line using String.split into columns
Create a Product item from the columns and add it to the list
Return the result list.

Aside note: it would be better to use price in int cents than in double because the floating-point arithmetics is known to be imprecise.

import java.io.*;
import java.util.*;
// ...

public static List<Product> readFile(String csvFile) throws Exception {
    List<Product> result = new ArrayList<>();
    try (BufferedReader br = new BufferedReader(new FileReader(csvFile))) {
        String line;
        while((line = br.readLine()) != null) {
            String[] cols = line.split("\\s*,\\s*"); // split by comma and optional spaces
            assert cols.length > 2;  // make sure the line contains at least 3 columns
            Product product = new Product(cols[0], cols[1], Double.parseDouble(cols[2]));
            result.add(product);
        }
    }
    catch(Exception e) {
        System.err.println(e.getMessage());
        throw e;
    }
   
    return result;
}

来源：https://stackoverflow.com/questions/65275606/is-there-any-ways-to-save-external-file-information-into-array-in-java

标签

java

arrays

arraylist

filereader