Do I need an actual file for it to compile?

Question about the task

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I tried many times on IntelliJ but it doesn't verify. The third and fourth requirements are not met. When I run on IntelliJ, I input random words from the keyboard, but it doesn't let me enter more than one line. If I press enter, It automatically ends and says "Process finished with exit code 0". But it doesn't output anything...I'm not sure if the problem is I need an actual file or it's something about my code. Help!

1. Read a file name from the console.
2. Read a set of numbers from the file.
3. Display only the even numbers, sorted in ascending order.

Example input:
5 8 -2 11 3 -5 2 10

Example output:
-2 2 8 10

Requirements:

The program must read data from the console.
The program must create a FileInputStream using the line read from the console.
The program should display data on the screen.
The program should display all of the even numbers read from the file, sorted in ascending order.
The program must close the input stream used to read the file (FileInputStream).

package com.codegym.task.task13.task1326; /* Sorting even numbers from a file */ import java.io.*; import java.util.ArrayList; import java.util.List; import java.util.Collections; public class Solution { public static void main(String[] args) throws IOException { FileInputStream fileLines = new FileInputStream(new BufferedReader(new InputStreamReader(System.in)).readLine()); BufferedReader reader = new BufferedReader(new InputStreamReader(fileLines)); List<Integer> list = new ArrayList<>(); while (Integer.parseInt(reader.readLine()) % 2 == 0 && reader.readLine() != null) { int lines = Integer.parseInt(reader.readLine()); list.add(Integer.parseInt(reader.readLine())); } fileLines.close(); Collections.sort(list); for (Integer a : list) { System.out.println(a); } } }

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Thang Za Thang

Level 18 , Melbourne, Australia

11 July 2020, 00:23

useful

BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String fileN = reader.readLine(); FileInputStream file = new FileInputStream(fileN); reader.close(); ArrayList<Integer> list = new ArrayList<>(); BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(file)); while(bufferedReader.ready()){ int number = Integer.parseInt(bufferedReader.readLine()); if(number % 2 == 0 ) { list.add(0,number); } } file.close(); bufferedReader.close(); Collections.sort(list); for(Integer x: list){ System.out.println(x); }

Angel Li

Level 18 , Fremont, United States

13 July 2020, 17:23

Thanks! It works now

Timboo

Level 16 , Shantou, China

4 August 2020, 06:52

it didn't work for me. Always mention need to use try...catch lol

Guadalupe Gagnon

Level 37 , Tampa, United States

3 July 2020, 19:39

useful

Every call to reader.readLine() reads the next number in the file:

// this line reads 2 numbers from the file
while (Integer.parseInt(reader.readLine()) % 2 == 0 && reader.readLine() != null) {
   // this line reads 1 number from the file
   int lines = Integer.parseInt(reader.readLine());
   // this line reads 1 number from the file
   list.add(Integer.parseInt(reader.readLine()));
}

this bit of code, each time it loops, reads 4 numbers from the file but will only add one. That is of course as long as the numbers that are read in as part of the while conditions return true because the loop ends otherwise.

Angel Li

Level 18 , Fremont, United States

4 July 2020, 17:46

Thanks, I changed my code to:

public class Solution {
    public static void main(String[] args) throws IOException {
        FileInputStream fileLines = new FileInputStream(new BufferedReader(new InputStreamReader(System.in)).readLine());
        BufferedReader reader = new BufferedReader(new InputStreamReader(fileLines));

        List<Integer> list = new ArrayList<>();
        String lines = reader.readLine();
        while (Integer.parseInt(lines) % 2 == 0 && reader.readLine() != null) {
            list.add(Integer.parseInt(lines));
            lines = reader.readLine();
        }
        fileLines.close();

        Collections.sort(list);
        for (Integer a : list) {
            System.out.println(a);
        }
    }
}

Is there anything else wrong with my code?

Guadalupe Gagnon

Level 37 , Tampa, United States

7 July 2020, 13:29

useful

Line 8 will not work. A 'while' loop will only continue looping as long as the condition (or conditions) return true. The first condition that is present in this loop is 'Integer.parseInt(lines) % 2 == 0' which checks if the number read in is even. If the number is odd then the loop will end and the code moves to line 12. I think you are attempting to filter out the odd numbers per the task, but this breaks the loop the very first odd number that is encountered. Also, the next condition 'reader.readLine() != null' checks if the value read in is not null. This is a problem because it does not save the value from readLine() to any variable. This will mean that the BufferedReader gets moved to the next line of the file but the data is lost. I suggest using this as the while loop condtion:

while (reader.ready())

This will return true (and keep the loop active) as long as there is more data to read inside the file, or false otherwise. You will also want to code in the 'readLine()' calls inside the loop. You can filter the odd numbers out by not adding them to the list inside the loop; or you can add all the numbers then only display the even numbers. The choice is up to you.

Angel Li

Level 18 , Fremont, United States

13 July 2020, 17:23

Thank you! It worked now!