Level 10

09.11.2020
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14comments

Hi Coders!

Question about the task

Resolved

What is my wrong?

Use the keyboard to enter numbers, and then calculate the arithmetic mean.
If the user enters -1, display the arithmetic mean of all entered numbers and end the program.
-1 should not be included in the calculation.

Here are some examples:
a) if you enter the numbers
1
2
2
4
5
-1
then we display
2.8

b) if you enter the numbers
4
3
2
1
-1
then we display
2.5

Hint: one of the solutions to this problem uses the following construct:

while (true) {
    int number = read the number;
    if (check whether the number is -1)
        break;
}

Requirements:

The program must read data from the keyboard.
The program should display data on the screen.
After entering -1, the program must correctly terminate.
If you sequentially enter the numbers 1, 2, 2, 4, 5 and -1, the program should display 2.8.
If you sequentially enter the numbers -100, 0, 100, and -1, the program should display 0.0.
If you sequentially enter the numbers 1 and -1, the program should display 1.0.
The displayed result should match the task conditions for any input data.

package com.codegym.task.task05.task0507; /* Arithmetic mean */ public class Solution { public static void main(String[] args) throws Exception { //write your code here InputStream keyboard = System.in ; Reader keyboardReader = new InputStreamReader(keyboard) ; BufferedReader input = new BufferedReader(keyboardReader) ; double i = 0 ; int x = 0 ; while (true) { int a = Integer.parseInt(input.readLine()) ; i =+ a ; x ++ ; if (a == -1) break; System.out.println(i/x) ; } } }

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Switch/Cypher

Level 25 , Bexleyheath, United Kingdom

9 November 2020, 13:06

First open BufferedReader like this:

BufferedReader keyboardInput = new BufferedReader(new InputStreamReader(System.in));

Second - check where your curly braces are. You don't want the print command in your while loop. Third - use IntelliJ it will REALLY help you, there are a number of other errors which IntelliJ would have flagged for you.

Switch/Cypher

Level 25 , Bexleyheath, United Kingdom

9 November 2020, 13:20

Give your variables meaningful names as well. Get in the habit of it. Don't call them 'x' or 'v'. Say what they do:

public static void main(String[] args) {

           double sum = 0;
           int inputs = 0;

           try (BufferedReader keyboardInput = new BufferedReader(new InputStreamReader(System.in))) {

               while (true) {
                   int currentInput = Integer.parseInt(keyboardInput.readLine());
                   sum += currentInput;
                   inputs++;
                   if (currentInput == -1)
                       break;
               }

               keyboardInput.close();

               System.out.println(sum / inputs);

           } catch (Exception e) {
               e.printStackTrace();
           }
       }

Here is some cleaned up code - don't worry about the try/catch, I'm just putting that in to show you what the 'finished' code might look like. Do look at the 'close' of the input stream though. CodeGym hasn't talked to you about this yet, but get used to doing it otherwise you will constantly forget later when you need to. Like I do.

Шарох

Level 10

9 November 2020, 13:29

I dont have any camputer or laptop :) So i should work for buy one. :)

Switch/Cypher

Level 25 , Bexleyheath, United Kingdom

9 November 2020, 13:32

Ah right - yes probably. As the course progresses you will find it really hard if you are doing things on a phone. IntelliJ is like super enhanced spellchecker for your code.

Шарох

Level 10

9 November 2020, 14:00

I tried for it .but it doesnt work also. It says : " BufferedReader class not found".

Switch/Cypher

Level 25 , Bexleyheath, United Kingdom

9 November 2020, 14:27

import java.io.BufferedReader;
import java.io.InputStreamReader;

You need both of those right at the top of the code.

Switch/Cypher

Level 25 , Bexleyheath, United Kingdom

9 November 2020, 14:29

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Solution {
    public static void main(String[] args) {

        double sum = 0;
        int inputs = 0;

        try (BufferedReader keyboardInput = new BufferedReader(new InputStreamReader(System.in))) {

            while (true) {
                int currentInput = Integer.parseInt(keyboardInput.readLine());
                sum += currentInput;
                inputs++;
                if (currentInput == -1)
                    break;
            }

            keyboardInput.close();

            System.out.println(sum / inputs);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Misiu

Level 41 , Gdansk, Poland

9 November 2020, 14:34

Very good explanations. As always from you. I admire. But: "-1 should not be included in the calculation."

Шарох

Level 10

9 November 2020, 14:47

Hi Misiu ! Yes, it doesnt work.And because of i dont understand what is try and catch i remove them.

Шарох

Level 10

9 November 2020, 14:49

Thank you so much ! I edited my code and removed " try and catch" .because i cant understand that. But still doent work.It need edit in mathematics maybe.