I have the solution but I do not understand - java help on CodeGym

Questions 1) what do they mean with the 'specified id' in this context? It seems like we have to create a method in which you can pass the int id? 2) what is this args[0] in this context? I only know it from the main method that you enter an argument(s) in the main method when you modify the main() 3) what is display.ed? Every product? As each productString starts with an int id so we're not looking for a specified int id? I actually do not understand this sentence: The program should search the file and display information related to the specified id passed as the first argument. => I know now after having seen the solution sort of what they mean.

package com.codegym.task.task18.task1822;
import java.io.*;

public class Solution {
       public static void main(String[] args) throws IOException {
        //step1: read a filename from the console
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String file = reader.readLine();
        reader.close();

        //step2: Create an inputStream for the file.
        //I wrap the inputStream in a bufferedReader as I want to use readLine() method
        BufferedReader reader2 = new BufferedReader(new FileReader(file));
        while (!reader2.readLine().isEmpty()) {
            String product = reader2.readLine();//here I read each product per line
            //and check if  the product has an id
            //TODO: The program should search the file and display information related to the specified id passed as the first argument.
            //what do they mean with the 'specified id' in this context?
            //what is this args[0] in this context? I only know it from the main method that you enter an argument(s) in the main method
            if (product.startsWith(args[0] + " ")) {
                //what does this display. Every product? As each productString starts with an int id
                System.out.println(product);
                break;
            }
      }
}

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Guadalupe Gagnon

Level 37 , Tampa, United States

11 January 2021, 16:35

solution

1) You should be displaying the specific line that has the same exact id as args[0] is. So if the program is started with the argument "123" (which would become args[0]), then the program should search the file for the line with the id "123". The file could be like this: 1 /*rest of product info*/ 5 /*rest of product info*/ 67 /*rest of product info*/ 123 /*rest of product info*/ 502 /*rest of product info*/ and with this example the program should output the fourth line. 2) args[0] is going to be whatever the program argument is when started. You will not know it before because it would be up to the end user, and could be anything only restricted by the fact the task says it is an int (could be a value between negative and positive 2.4 billion). 3) it should only display the line where the id matches the argument that the program is started with (args[0]) To enter program arguments for testing in intelliJ you do so by editing the configurations:

(see pic)Here you enter the arguments. It will fill the args array splitting the arguments by each space. If you want one argument that has spaces to be together (as in not split), then enclose that in quotation marks. So if you enter this as the program args: 123 435 12354 "learning java" is fun And then output the array:

System.out.println(Arrays.toString(args));

The resulting array would have 6 values that would be: {123, 435, 12354, learning java, is, fun}

Liliane Top Backend Developer at Procura

11 January 2021, 17:57

I tried it and I never knew that it should be space separated I used comma's and it didn't work. Now I know why. And also your example makes it 100% clear!!!

I have the solution but I do not understand it