whats wrong with the code?

Question about the task

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Why its not working with simple string? i know we can use either list or map or other such type but what i am missing with the string?

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; import java.io.File; import java.io.IOException; import java.io.FileNotFoundException; public class Solution { public static void main(String[] args) throws IOException,FileNotFoundException{ String line = ""; String newString = ""; String oldContent = ""; String oldString = ""; BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String fileName = br.readLine(); File originalFile = new File(fileName); br.close(); FileInputStream is = new FileInputStream(fileName); //ArrayList<String> list = new ArrayList<>(); br = new BufferedReader(new InputStreamReader(is)); if(args.length != 0 ){ if(args[0].equals("-u")){ line = br.readLine(); while (line != null) { //String[] lineArray = line.split(" "); if((line.substring(0,8).trim()).equals(args[1])){ oldString = line; //}else{ oldContent = oldContent + line + System.lineSeparator(); } line = br.readLine(); } StringBuilder sb = new StringBuilder(); //sb.append(String.format("%-8s",args[1])); sb.append(String.format("%-8s%-30s%-8s%-4s",args[1],args[2],args[3],args[4])); sb.append("\n"); newString = sb.toString(); newString = oldContent.replace(oldString,newString); //FileWriter writer = new FileWriter(fileName); FileOutputStream fileOut = new FileOutputStream(fileName); fileOut.write(newString.getBytes()); fileOut.close(); //is.close(); br.close(); } }else if(args[0].equals("-d")){ String s = ""; String stringAfterDeletion = ""; FileOutputStream os = new FileOutputStream(fileName); if ((s = br.readLine()) != null) { //String[] lineArray = s.split(" "); if(!(s.substring(0,8).trim()).equals(args[1])){ //bw.write(s + System.getProperty("line.separator")); stringAfterDeletion = stringAfterDeletion + s + System.lineSeparator(); } } os.write(stringAfterDeletion.getBytes()); os.close(); is.close(); br.close(); } } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

27 November 2019, 16:00

solution

#1 it looks like you were testing by removing the "else" at line 39, add this back in. #2 Now that the if-else is back, there is a bug where if the line contains the id, the line is never added to "oldContent". This will cause problems at line 50 when newString is supposed to be oldContent with the updated line replacing the content to be updated. #3 do not append a new line character to the updated line. If the updated line is in the middle of the file this is going to leave a blank line following it. Either that or add the line seperator to the end of oldString. #4 Line 60 has the else-if following the wrong curley bracket. If you follow the line all the way up you will find that it connects to line 29. This reads:

if(args.length != 0 ){
  // code
}else if(args[0].equals("-d"))

So if args equals 0 then it will check if args[0] and throw an index out of range exception #5 once #4 is corrected, at line 65 you open a new OutPutStream. At this point a new file is created at this point which will erase all the data in the file before the loop at line 66 that reads the data. You will want to move line 65 until after you finish reading in the data. #6 Line 66 should be a while loop, not an if statement

Rupa Joshi

Level 29 , Tokyo, Japan

5 December 2019, 01:52

thanks for your detailed explanation. I don't remember how many ways I tried this and doing that might have done these silly mistakes, as I was not getting only the update file option I guess changed something and delete was not also working. I think when I wrote this code, the only problem could be the one which you told about adding a new line character I guess. Thanks for the help again.