I could probably solve this in another way, but why doesn't this solution work?

Question about the task

Resolved

This clearly has some problems but I don't know why. I had a look at the while loops in the lessons where they were explained, but can't see the problem.

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 */ import java.io.BufferedReader; import java.io.InputStreamReader; public class Solution { public static void main(String[] args) throws Exception { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); int number = Integer.parseInt(reader.readLine()); int count = 0; int total = 0; double result; while (number != -1) { number = Integer.parseInt(reader.readLine()); total += number; count++; } if (count != 0) { result = total / count; } result = 0; System.out.println(result); } }

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Ashish Methani

Level 11 , Raipur, India

28 April 2019, 09:42

First number gets ignored in your program as you have used inputstreamreader outside the while loop in line 6 i.e. double number = Double.parseDouble(reader.readLine()); This line should be removed. And also it makes result = 0 just before printing it.. notice this result = 0; System.out.println(result);

Anastasia Falcon

Level 8 , Rio de Janeiro, Brazil

28 April 2019, 11:31

the result = 0 was intended as a part of if statement. If count is not zero, then calculations, otherwise - result should be displayed as 0. But anyway, I've already deleted that and it still doesn't work.

Anastasia Falcon

Level 8 , Rio de Janeiro, Brazil

28 April 2019, 11:33

Thanks a lot for help!

Ashish Methani

Level 11 , Raipur, India

28 April 2019, 08:45

import java.io.BufferedReader; import java.io.InputStreamReader; public class Main { public static void main(String[] args) throws Exception { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); //String x = reader.readLine(); int number = 0; int count = 0; double result = 0; int total = 0; while(true) { number = Integer.parseInt(reader.readLine()); if (number == -1) { break; } total += number; count++; result = (double)total / count; } System.out.println(result); } }

Anastasia Falcon

Level 8 , Rio de Janeiro, Brazil

28 April 2019, 08:58

The code looks like this right now and doesn't work correctly. I don't really get what's wrong. I changed the type for double just to try if it changes anything. import java.io.BufferedReader; import java.io.InputStreamReader; public class Solution { public static void main(String[] args) throws Exception { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); double number = Double.parseDouble(reader.readLine()); int count = 0; double result = 0; double total = 0; while(true) { number = Double.parseDouble(reader.readLine()); if (number == -1) { break; } total += number; count++; } if (count != 0) { result = total / count; } result = 0; System.out.println(result); } }

Anastasia Falcon

Level 8 , Rio de Janeiro, Brazil

28 April 2019, 02:51

Now my code looks like this and doesn't pass testing, what's wrong?: package com.codegym.task.task05.task0507; /* Arithmetic mean */ import java.io.BufferedReader; import java.io.InputStreamReader; public class Solution { public static void main(String[] args) throws Exception { BufferedReader reader = new BufferedReader(new InputStreamReader(System.in)); String x = reader.readLine(); int number = Integer.parseInt(x); int count = 0; double result = 0; int total = 0; while(true) { number = Integer.parseInt(reader.readLine()); if (number == -1) { break; } total += number; count++; result = number / count; } System.out.println(result); } }

Ashish Methani

Level 11 , Raipur, India

27 April 2019, 07:42

while (number != -1) { total += number; count++; number = Integer.parseInt(reader.readLine()); } Once number is read from keyboard it should immediately enter in while condition loop to avoid -1 to be counted.. Also initialize the result variable

Anastasia Falcon

Level 8 , Rio de Janeiro, Brazil

27 April 2019, 11:52

"Once number is read from keyboard it should immediately enter in while condition loop to avoid -1 to be counted.. Also initialize the result variable" so, just the way the loop works doesn't cover that? I thought, if the first entered number is -1, the loop just won't start (cause the condition is not met), the method will skip it and jump to printing results

Anastasia Falcon

Level 8 , Rio de Janeiro, Brazil

27 April 2019, 12:00

ok, I read some more about loops and I guess instead of making a loop with a condition I was supposed to instead make an infinite loop with a break statement for number = -1 ? this is why tis was in the hint: while (true) { int number = read the number; if (check whether the number is -1) break; } I didn't quite get why it looked like that, but now I get it