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Question about the task

Prices

Java Core, Level 8, Lesson 11

Under discussion

The output seems to be correct...I'm going crazy! Thanks!

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.nio.file.Files; import java.util.ArrayList; import java.util.List; public class Solution { public static void main(String[] args) throws Exception { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String fileName = br.readLine(); if (args.length > 0) { File file = new File(fileName); BufferedReader reader = new BufferedReader(new FileReader(file)); String id = "", productName = "", price = "", quantity = "", data = ""; int i = 0, idI = 0; String st; List<String> lines = new ArrayList<String>(); while ((st = reader.readLine()) != null) { lines.add(st); if (st.substring(0, 8).contains(" ")) { id = st.substring(0, st.substring(0, 8).indexOf(" ")); } else { id = st.substring(0, 8); } i = Integer.parseInt(id); if (i > idI) { idI = i; } } reader.close(); id = padRight(String.valueOf(idI + 1), 8); productName = padRight(args[1], 30); price = padRight(args[2], 8); quantity = padRight(args[3], 4); data = id + productName + price + quantity; lines.add(data); BufferedWriter writer = new BufferedWriter(new FileWriter(fileName)); for (int x = 0; x < lines.size() ; x++) { writer.write(lines.get(x)); writer.newLine(); } writer.close(); } } public static String padRight(String s, int n) { return String.format("%-" + n + "s", s); } }

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Wei Cui

Level 39 , Newark, United States

28 March 2020, 17:07

public class Solution {
    public static void main(String[] args) throws Exception {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        String fileName = bufferedReader.readLine();

        //check if args is null and first args if -c
        if(args.length > 0) {
            switch (args[0]) {
                case "-c":
                    addLine(fileName, args);
                    break;
            }
        }

    }


    public static void addLine(String fileName, String[] args) {
        //read args argument
        String productName = args[1];
        String price = args[2];
        String quantity = args[3];

        ArrayList<String> lineList = new ArrayList<>();
        int maxId = 0;

        //put all line into list and find out maximum number
        try {
            BufferedReader br = new BufferedReader(new FileReader(fileName));

            while (br.ready()) {
                String line = br.readLine();
                lineList.add(line);
                //use trim method erase space
                int id = Integer.parseInt(line.substring(0,8).trim());
                // return maxid = id if id greater than maxid
                maxId = maxId < id ? id : maxId;
            }
            br.close();

            //created new maximum number and put new line into list
            maxId++;
            lineList.add(String.format("%-8s%-30s%-8s%-4s", maxId, productName, price, quantity));
            FileWriter fw = new FileWriter(fileName);

            //write all line back to file
            for (String line : lineList)
                fw.write(line + "\r\n");
            fw.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}