Program displays too many lines

Question about the task

Sorting even numbers from a file

Java Core, Level 3, Lesson 11

Under discussion

Anybody knows whats wrong?

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; import java.io.*; import java.util.*; /* Sorting even numbers from a file */ public class Solution { public static void main(String[] args) throws IOException{ //write your code here BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String fileName = br.readLine(); ArrayList<Integer> list = new ArrayList<>(); InputStream inStream = new FileInputStream(fileName); while(inStream.available() > 0){ int data = inStream.read(); if(Character.isDigit(data) && isEven(data)) list.add(data); } inStream.close(); Collections.sort(list); for(int e : list) System.out.print(e); } static boolean isEven(int num){ if(num % 2 == 0) return true; return false; } }

Comments (2)

Popular
New
Old

You must be signed in to leave a comment

Gellert Varga

Level 23 , Szekesfehervar, Hungary

30 May 2021, 21:10

In line 12, you use Reader, which can read characters one by one - or a whole line. Unfortunately, in line 17 you are using InputStream, which reads only bytes, not the actual characters. Wrap this InputStream into a Reader in the same way as you did in line 12. (In place of System.in, put inside your own variable called inStream.) For example, if you read in the character 2 (i.e., TWO as a mathematical number), a Reader will return this read character: 2. If you read in the same number 2 with an InputStream, not a Reader, you will not get the number itself, but the byte that represents the number 2 to the computer. This byte will show us the number 50 (in decimal system). Which can be read from the ASCII code tables below: https://theasciicode.com.ar/ https://en.wikipedia.org/wiki/ASCII 1 = 49 2 = 50 3 = 51 A = 65 etc.

Thomas

Level 41 , Bayreuth, Germany

28 May 2021, 11:45

you're reading character for character and not the whole numbers. If a line has the content 1234\n then you read the numbers 49 50 51 52 13 (without the spaces and the 13 at the end depends on your system). 50 and 52 are even and those you add to the output. You need to read the entire line instead. And probably you see now, too, why the validation may complain about to many lines.