CodeGym/Help with Java Tasks/String out of bounds ???

Level 22

23.10.2020
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8comments

String out of bounds ???

Question about the task

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Hi, I'm still working on this task but I'm getting a string out of bounds error on line 33 and can't figure out why. Help will be appreciated. Thanks.

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.ArrayList; public class Solution { public static void main(String[] args) throws IOException { //BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); //String fileName = reader.readLine(); updateProduct("/home/seferi/test", "2", "productName", "43.8", "322"); } public static void updateProduct(String fileName, String id, String productName, String price, String quantity) throws IOException { ArrayList<String> lines = new ArrayList<>(); ArrayList<Product> productList = new ArrayList<>(); FileInputStream inputStream = new FileInputStream(fileName); BufferedReader lineReader = new BufferedReader(new InputStreamReader(inputStream)); String data; while ((data = lineReader.readLine()) != null) { lines.add(data); } inputStream.close(); lineReader.close(); for (String line : lines) { String oldId = line.substring(0, 8).trim(); String oldProductName = line.substring(9, 38).trim(); String oldPrice = line.substring(39, 46).trim(); String oldQuantity = line.substring(47, 50).trim(); productList.add(new Product(oldId, oldProductName, oldPrice, oldQuantity)); } FileOutputStream outputStream = new FileOutputStream(fileName); for (Product product : productList) { if (id.equals(product.getId())) { product.setProductName(productName); product.setPrice(price); product.setQuantity(quantity); } String productString = String.format("%-8s%-30s%-8s%-4s\n", product.getId(), product.getProductName(), product.getPrice(), product.getQuantity()); outputStream.write(productString.getBytes()); } outputStream.close(); } public static void deleteProduct(String fileName, String id) throws IOException { ArrayList<String> lines = new ArrayList<>(); ArrayList<Product> productList = new ArrayList<>(); FileInputStream inputStream = new FileInputStream(fileName); BufferedReader lineReader = new BufferedReader(new InputStreamReader(inputStream)); String data; while ((data = lineReader.readLine()) != null) { lines.add(data); } inputStream.close(); lineReader.close(); for (String line : lines) { String oldId = line.substring(0, 8).trim(); String oldProductName = line.substring(8, 30).trim(); String oldPrice = line.substring(30, 38).trim(); String oldQuantity = line.substring(38, 42).trim(); productList.add(new Product(oldId, oldProductName, oldPrice, oldQuantity)); } FileOutputStream outputStream = new FileOutputStream(fileName); productList.removeIf(product -> id.equals(product.getId())); for (Product product : productList) { String productString = String.format("%-8s%-30s%-8s%-4s\n", product.getId(), product.getProductName(), product.getPrice(), product.getQuantity()); outputStream.write(productString.getBytes()); } outputStream.close(); } public static class Product { private String id; private String productName; private String price; private String quantity; public String getId() { return id; } public void setId(String id) { this.id = id; } public String getProductName() { return productName; } public void setProductName(String productName) { this.productName = productName; } public String getPrice() { return price; } public void setPrice(String price) { this.price = price; } public String getQuantity() { return quantity; } public void setQuantity(String quantity) { this.quantity = quantity; } public Product(String id, String productName, String price, String quantity) { this.id = id; this.productName = productName; this.price = price; this.quantity = quantity; } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

23 October 2020, 16:28

solution

Lets take a look, here are some tips and maybe corrections that will pass: #1 lines 20-38 and lines 53-70 are exactly the same. I would suggest moving them all to a method. #2 Also the outputting of the data could be moved to a method to be done after the "-c" or "-u" methods do what they are supposed to. Here is some abbreviated code of what I mean for the :

-d method (...) {
    ArrayList<Product> productList = getProductList(fileName); // method that combines point #1
   // code here to delete product
   outputProducts(productlist, fileName); // method that combines point#2
}

-u method (...) {
    ArrayList<Product> productList = getProductList(fileName);
   // code here to update product
   outputProducts(productlist, fileName);
}

#3 I hope that the main method checks args for the appropriate values. The code above does not show that though I am sure that this help post was made while you were still working on the task. #4 on the output, I use a technique like like below to ensure that no extra lines are added to the file:

ArrayList<> outputData = /* some array list with multiple output values*/;
Iterator iter = outputData.iterator(); // i like iterators for this
if(iter.hasNext()) { // checks if List has at least 1 value
   OutputStream os = /*some stream*/;
   os.write(iter.next()); // writes first
   while(iter.hasNext()) // as long as there are more values
      os.write("\n" + iter.next()); // it writes the rest starting with a new line
   os.close();
}

Now your output file won't end with a blank line at the end

Guadalupe Gagnon

Level 37 , Tampa, United States

23 October 2020, 16:32

#5 If you override the toString() method in the product class, you can just output product.toString(). so:

// in the Product class:
public String toString() {
    return String.format("%-8s%-30s%-8s%-4s\n", product.getId(),
       product.getProductName(), product.getPrice(), product.getQuantity())
}

// then in the Solution class where ever you do the output just use this:
output.write(product.toString().getBytes());

Seferi

Level 22 , United Federation of Planets

23 October 2020, 20:38

Thanks mate, I'm trying to implement iterator to the task but I'm having trouble overriding toString method because it's not static I can't use Product.getId() or this.getId()... Any suggestions ?

Guadalupe Gagnon

Level 37 , Tampa, United States

23 October 2020, 20:51

I copied and pasted that directly from your code where it was written in the method. I should modified it so it actually worked in the Product class. Here it is as it should be in the Product class:

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

Seferi

Level 22 , United Federation of Planets

23 October 2020, 22:08

Alright, I implemented everything and tested, it works for me but fails the tests.. Couldn't paste the code here so I opened a new help request: https://codegym.cc/help/13639 I really appreciate the help..

Guadalupe Gagnon

Level 37 , Tampa, United States

23 October 2020, 13:19

useful

The problem is going to be with the input file ("/home/seferi/test"). Either the 'products' in the file are not spaced properly, or more likely there are lines at the bottom of the file. Example: " product#1 /n product#2 /n product#3 /n "<---- this would be a blank line Because blank lines do not equal null, the loop on lines 26-28 would add it to the lines array and then your exception would occur when it reaches that line. You can easily test for what input line is causing the error by doing this:

for (String line : lines) {
   System.out.println(line); // <- this will show you line creates the error.
   String oldId = line.substring(0, 8).trim();
   String oldProductName = line.substring(9, 38).trim();
   String oldPrice = line.substring(39, 46).trim();
   String oldQuantity = line.substring(47, 50).trim();
   productList.add(new Product(oldId, oldProductName, oldPrice, oldQuantity));
}

Seferi

Level 22 , United Federation of Planets

23 October 2020, 15:57

Thanks mate. There was an extra line on my test file. I don't get the error anymore but it still doesn't pass. And I can't find the reason.. Do you have any ideas ?

Misiu

Level 41 , Gdansk, Poland

23 October 2020, 16:12

useful

substring(a, b) ---> indexes from a to b-1