I don't understand why it won't verify - I am trying to update the file but it removes all the content - "-u", "19847 ", "Swim trunks, blue ", "159.00 ", "20 "

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The program won't verify, I have tested it with a file that has the example given and the argument "-u", "19847 ", "Swim trunks, blue ", "159.00 ", "20 ". The program runs but the file is empty. I don't understand why it is empty because I have checked the program and it seems ok.

CrUD for a table inside a file
Read a file name for CrUD operations from the console

The program runs with one of the following sets of arguments:
-u id productName price quantity
-d id

Argument values:
where id is 8 characters
productName is 30 characters
price is 8 characters
quantity is 4 characters
-u updates the data for the product with the specified id
-d performs the physical deletion of the product with the specified id (all data related to the passed id)

The file data is stored in the following order (without separating spaces):
id productName price quantity
Each data field is padded with spaces up to its length

Example:
19847 Swim trunks, blue 159.00 12 198479 Swim trunks, black with printe173.00 17 19847983Snowboard jacket with reflecti10173.991234

Requirements:

The program should read a file name for CrUD operations from the console.
When you run the program without arguments, the product list must remain unchanged.
When the program is started with the arguments "-u id productName price quantity", the product information in the file should be updated.
When the program is started with the arguments "-d id", the line for the product with the specified id should be removed from the file.
The file streams must be closed.

package com.codegym.task.task18.task1828; /* Prices 2 */ import java.io.*; import java.util.HashMap; import java.util.Map; import java.util.TreeMap; public class Solution { public static class Product { int id; String name; String price; String quantity; @Override public String toString(){ return String.format("%-8d%-30s%-8s%-4s", id, name, price, quantity); } public Product(int id, String name, String price, String quantity) { this.id = id; this.name = name; this.price = price; this.quantity = quantity; } public int getId() { return this.id; } public void setId(int id){ this.id = id; } } public static void main(String[] args) throws Exception { if (args.length == 0) return; BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in)); String fileName = bufferedReader.readLine(); bufferedReader.close(); BufferedReader bufferedFileReader = new BufferedReader(new FileReader(fileName)); Map<Integer, Product> productMap = new TreeMap<>(); while (bufferedFileReader.ready()) { String productFromFile = bufferedFileReader.readLine(); int id = Integer.valueOf(productFromFile.substring(0, 8).trim()); String name = productFromFile.substring(8, 38).trim(); String price = productFromFile.substring(38, 46).trim(); String quantity = productFromFile.substring(46, 50).trim(); Product product = new Product(id, name, price, quantity); productMap.put(id, product); } for (Map.Entry<Integer, Product> entry : productMap.entrySet()){ System.out.println(entry.toString()); } bufferedFileReader.close(); BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(fileName)); switch (args[0]) { case "-u": if (args[1] == null || args[2] == null || args[3] == null || args[4] == null) return; Product productUpdate = productMap.get(Integer.valueOf(args[1])); productUpdate.name = args[2]; productUpdate.price = args[3]; productUpdate.quantity = args[4]; productMap.replace(productUpdate.id, productUpdate); for (Map.Entry<Integer, Product> entry : productMap.entrySet()){ bufferedWriter.write(entry.toString()); bufferedWriter.write("/n"); } case "-d": if (args[1] == null || args[2] == null || args[3] == null || args[4] == null) return; productMap.remove(args[1]); for (Map.Entry<Integer, Product> entry : productMap.entrySet()){ bufferedWriter.write(entry.toString()); } } bufferedWriter.close(); } }

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Nouser

Level 36 , Germany

2 February 2021, 15:16

solution

there are several problems.. - break in case missing... so -d is getting executed when -u is matching - entry.toString.. entry is a key value pair. You just want to output the value (it already has the key in it) better would be just to iterate over the values like (in -u and -d as d has the same and even more problems)

for (Product product : productMap.values()){
    bufferedWriter.write(product.toString());
    bufferedWriter.write("\n");
}

- oh, I already fixed above the /n and replaced it with \n - -d clause is having problems cause you just have two arguments here - in addition to that you should parse args[1] to an Integer - maybe I'm missing something, don't know anymore what else I have changed ;), but you should be able to make it from here, btw, the Product class is great... you're already thinking in objects ;) you could beef it up a little and give the constructor jest the read string and let it do the rest like

public Product(String s) {
    id = Integer.valueOf(s.substring(0, 8).trim());
    name = s.substring(8, 38).trim();
    price = s.substring(38, 46).trim();
    quantity = s.substring(46, 50).trim();
}

(just moved your code up into the Product class and gave it some more functionality)

Andrei

Level 41

2 February 2021, 17:03

public class Solution {

        public static class Product {
        int id;
        String name;
        String price;
        String quantity;

            @Override
            public String toString(){
                return String.format("%-8d%-30s%-8s%-4s", id, name, price, quantity);
            }

             public Product(String rowReadFromFile) {
                  id = Integer.valueOf(rowReadFromFile.substring(0, 8).trim());
                  name = rowReadFromFile.substring(8, 38).trim();
                  price = rowReadFromFile.substring(38, 46).trim();
                  quantity = rowReadFromFile.substring(46, 50).trim();
             }
        }

        public static void main(String[] args) throws Exception {
            if (args.length == 0) return;

            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
            String fileName = bufferedReader.readLine();
            bufferedReader.close();

            BufferedReader bufferedFileReader = new BufferedReader(new FileReader(fileName));

            Map<Integer, Product> productMap = new LinkedHashMap<>();

            //testing is correct, products print accordingly
            while (bufferedFileReader.ready()) {
                String productFromFile = bufferedFileReader.readLine();

                Product product = new Product(productFromFile);
                productMap.put(product.id, product);
            }

            bufferedFileReader.close();

            BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(fileName));

Andrei

Level 41

2 February 2021, 17:03

switch (args[0]) {
                case "-u":
                        Product productUpdate = productMap.get(Integer.valueOf(args[1]));
                        productUpdate.name = args[2];
                        productUpdate.price = args[3];
                        productUpdate.quantity = args[4];
                         for (Product product : productMap.values()){
                        bufferedWriter.write(product.toString());
                        bufferedWriter.write("\n");
                        }
                        break;

                case "-d":
                    productMap.remove(Integer.valueOf(args[1]));
                    for (Product product : productMap.values()){
                        bufferedWriter.write(product.toString());
                        bufferedWriter.write("\n");
                    }
                    break;
            }
            bufferedWriter.close();
        }
}

Andrei

Level 41

2 February 2021, 17:08

Very nice observations, thank you very much. 😁 I also noticed that Mentor kept asking for the products to be put back in the same order, so I changed the TreeMap to a LinkedHashMap so they retain the same order. Even though, in the list, the products are ordered naturally by id so I assumed this order would be kept using a TreeMap. Anyway, it checked. Nice trick with putting the variable inside the constructor, makes it cleaner. 😀 Regarding the product class, I'll admit, in the beginning I struggled a bit to find a way of storing the information but then I looked at the previous similar exercise and saw that there objects were used so I got the idea from there 😅

Guadalupe Gagnon

Level 37 , Tampa, United States

2 February 2021, 14:47

useful

Both of the write loops, lines 76-79 and 84-86 are writing the each Map.Entry instead of each Product. You will want to change those to write the correct object. Remove lines 70 and 82, this check is not needed and line 82 will crash the program with a NullPointerException when trying to access an index that does not exist. Line 83 is going to be a problem too because args[1] is a String and the keys of the Map are Integers. You don't need line 75. When you pull the object from the map one line 71 you are not getting a clone of that object, you are working with the same object that still resides in the Map. Line 75 will then replace the object with itself, which is not needed. Line 85 is going to put all the products on one line in the file.

Andrei

Level 41

2 February 2021, 17:05

Oh, nice catch with the write loops, thanks. That check was to see if the argument is introduced correctly. Granted, for the removal of the object (-d case) the check was useless or maybe should've been reduced to only args [1] ? For line 83 yeah, I forgot to add the Integer.valueOf. Regarding line 75 good point, didn't think of that! Thank you.