What is wrong in my formula?

Question about the task

Spaces

Java Core, Level 8, Lesson 11

Under discussion

Code below:

The first parameter of the main method is a file name.
Display the ratio of the number of spaces to the number of all characters. For example, 10.45.
1. Count all the characters (n1).
2. Count the spaces (n2).
3. Display n2/n1*100, rounding to 2 decimal places.
4. Close the streams.

Requirements:

You don't need to read anything from the console.
Create a stream to read from the file passed as the first argument of the main method.
Calculate and display the ratio of the spaces to all characters in the file.
The displayed value must be rounded to 2 decimal places.
The stream used to read the file must be closed.

package com.codegym.task.task18.task1817; /* Spaces */ import java.io.FileInputStream; import java.io.IOException; public class Solution { public static void main(String[] args) { int n1 = 0; int n2 = 0; try (FileInputStream fis = new FileInputStream(args[0])){ while (fis.available() > 0){ int data = fis.read(); if(data == 32){ n2++; }else{ n1++; } } }catch (IOException ioe){ } double d = Math.round((n2/(double)n1*100)*100)/100d; System.out.println(d); } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

10 March 2020, 18:35

The problem is that you are counting spaces and everything else separately. Take for example some random bytes: [1,2,3,1,3,1] and you wanted to know the ratio or byte 1 to every other byte. The correct way to figure that out is to divide the number of ones (3) by the number of total bytes (6). The code above would divide the number of ones by the number of other bytes (3). Tips: - fis.available(), before anything is read in, gives you the count of total bytes. You wouldn't need to specifically count them. - While you can do things the way you did above, when using streams, reading all the bytes in one chunk using a buffer and processing them afterwards is a LOT faster than reading each byte individually. To give you an idea I timed your code using a file that had 158047 bytes in it. It processed it all and gave an answer in 1419 milliseconds (1.4 seconds). I then rewrote lines 16-23 so that it to read all the bytes at once and then used a loop to count the number of spaces (byte 13). It gave an answer in 4 milliseconds.