Why am I getting 1.0 in mean for 1,2,2,4,5

Question about the task

Resolved

I'm really stuck on this one. I'have tried many different solutions without any luck... Please help me on this one my fellow CodeGymnasts

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.*; public class Solution { public static void main(String[] args) throws Exception { //write your code here BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); String input = br.readLine(); int numbers = Integer.parseInt(input); int sum = 0; int counter = 0; double mean = 0.0; // test stoppIT boolean stoppIT = false; while(!stoppIT){ if (input.equals("-1")){ break; } sum = sum + numbers; input = br.readLine(); counter++; stoppIT = input.equals("-1"); } if (mean <= 0.0){ System.out.println(mean); }else{ mean = sum/counter; System.out.println(mean); } } }

Comments (7)

Popular
New
Old

You must be signed in to leave a comment

JJSS

Level 8 , Monterrey, Mexico

15 December 2018, 16:03

when you divide two int numbers ... int / int ...the result will take out the fractional part. Ej...3/2 = 1

Khurram

Level 16 , Lahore, Pakistan

15 December 2018, 08:45

1. in line 33, input is not converted to Integer, the inputs all remain String type 2. the inputs are not moved to numbers variable, in line 32 sum = sum + numbers, here numbers is never updated inside the loop, the input taken at line 16 is repeatedly being added in sum 3. mean variable is initialized to 0.0 but it is not updated after the loop, so in line 38, mean will always be 0.0 and it will execute the print command and show 0.0, you need to calculate mean right after the loop 4. sum and counter are integer variables, and mean is double, there is difference in the data types of the operators, hence it will display unexpected results, it is better if sum and counter are also made double 5. in line 37, the if statement is not required, you can simply calculate mean and display it, regardless of its value

Iasu

Level 18 , Norway

15 December 2018, 12:18

hi thx for your answer!

Guadalupe Gagnon

Level 37 , Tampa, United States

14 December 2018, 22:52

solution

I rewrote your code to simplify, using notes. Nothing advanced here, though there are some techniques that could be helpful to you in the future:

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int sum = 0;
int counter = 0;
double mean;

for(;true;counter++){ // for loop, written like this, can keep a counter for you
   String input = br.readLine(); // read a number in as a string

   if (input.equals("-1")) // check string if it is -1, if it is exit loop
      break;

   int numbers = Integer.parseInt(input); // convert string to int

   sum += numbers; // short hand of sum = sum + numbers
}

mean = (double)sum/counter; // calculate the mean (make sure to convert the ints to double first
System.out.println(mean); // output

Guadalupe Gagnon

Level 37 , Tampa, United States

14 December 2018, 22:54

I really just made your while loop a for loop, moved a couple of lines, and deleted unnecessary code. This should satisfy the conditions, though I am not able to verify because mine is closed. Your big issue was how your loop was formed and the counter variable specifically. It only started counting after you entered the second number, which made your answers off by 1. You may have been able to solve it by making line 18 int counter = 1;. Your other problem was line 37 always evaluated to true because you did nothing to change the variable mean before then. Your code would always display zero no matter what.

Iasu

Level 18 , Norway

15 December 2018, 12:25

thnx man! Very compact, and few lines is good! I have one question for you my man! The for statement, I thought it took only three expressions, but in your example, it takes a boolean value and a variable. Does it say in a way --> If true --> count++?

Guadalupe Gagnon

Level 37 , Tampa, United States

15 December 2018, 15:30

I like to think of for loops like this: the first expression is what happens before the loop starts and only once, the second statement is what evaluates to keep the loop going, and the third is what executes after each cycle. (First; second; third). The thing is none of these are required. You can run a for loop like this:

for ( ; ; ) \\ this is an infinite loop