help please, can't verify

Question about the task

Prices

Java Core, Level 8, Lesson 11

Resolved

I tested it and the result seems fine, and I even deleted the last " " (space), but still can't be verified...

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

The program is started with the following arguments:
-c productName price quantity

Argument values:
where id is 8 characters.
productName is 30 characters.
price is 8 characters.
quantity is 4 characters.
-c adds the product with the specified parameters to the end of the file, and generates an id by incrementing the maximum id found in the file.

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.

Before adding a new line, re-write all of its contents to the file.

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.
The Solution class should not use static variables.
When you run the program without arguments, the product list must remain unchanged.
When the program is run with the arguments "-c productName price quantity", a new line with the corresponding product should be added to the end of the file.
The product must have the next id after the maximum id found in the file.
The format of the new product line must precisely match that format specified in the task.
The file streams must be closed.

package com.codegym.task.task18.task1827; /* Prices */ import java.io.*; import java.util.ArrayList; import java.util.Collections; import java.util.Scanner; public class Solution { public static void main(String[] args) throws Exception { Scanner scanner=new Scanner(System.in); String name=scanner.nextLine(); InputStream file=new FileInputStream(name); if(args.length!=0) { BufferedReader bf = new BufferedReader(new InputStreamReader(file)); String line; ArrayList<Integer> idList = new ArrayList<>(); ArrayList<String> lines = new ArrayList<>(); while ((line = bf.readLine()) != null) { idList.add(getId(line)); lines.add(line); } file.close(); BufferedWriter bw = new BufferedWriter(new FileWriter(name)); for (String l : lines) { bw.write(l); bw.newLine(); } bw.close(); int id = Collections.max(idList) + 1; char[] ida = String.valueOf(id).toCharArray(); char[] namea = args[1].toCharArray(); char[] pricea = args[2].toCharArray(); char[] quantitya = args[3].toCharArray(); write(ida, 8, name); write(namea, 30, name); write(pricea, 8, name); write(quantitya, 4, name); } } public static int getId(String line) { char[] array=line.toCharArray(); StringBuilder sb=new StringBuilder(); for (int i=0; i<8; i++) { if (array[i]==' ') break; sb.append(array[i]); } return Integer.parseInt(sb.toString()); } public static void write(char[] chars, int n, String outname) throws IOException { OutputStream out=new FileOutputStream(outname,true); for (int i=0; i<chars.length; i++) { out.write((byte)chars[i]); } if (chars.length<n && n!=4) { out.write(' '); } out.close(); } }

Comments (3)

Popular
New
Old

You must be signed in to leave a comment

Bill Wu

Level 29 , Wellington, New Zealand

21 March 2019, 22:13

The solution has to use only one outputstream to pass, in my original code there is an unnecessary bufferwriter

Guadalupe Gagnon

Level 37 , Tampa, United States

19 March 2019, 15:43

As far as I can tell your code does not pad the data from the command line arguments, this is the only difference from the operation of my code and your code. It does say in the requirements that "Each data field is padded with spaces up to its length.", but i don't think that applies to the data in the program arguments, as silly as that seems. Try changing the write method to this and see if it works:

public static void write(char[] chars, int n, String outname) throws IOException {
        OutputStream out=new FileOutputStream(outname,true);
        for (int i=0; i<n; i++) {
            if (i >= chars.length) {
                out.write(' ');
            }else
                out.write((byte)chars[i]);
        }

        out.close();
}

Bill Wu

Level 29 , Wellington, New Zealand

19 March 2019, 21:02

Thanks for your help. I misunderstood the requirement of the padding space, I thought they only need one. But I still fail the requirement of When the program is run with the arguments "-c productName price quantity", a new line with the corresponding product should be added to the end of the file. Can't figure out why because it does add the new data at the end with a new line.