Logical error in loop program

Question

import java.util.Scanner; 
public class Unit2Err2{ 
  public static void main( String[] args ){ 
    Scanner scan = new Scanner(System.in);                    
    double sum = 0;                                             
    double count = 0;
    double in = scan.nextDouble();                                                                      
    while (scan.nextDouble()!= 0){                                           
      sum = sum + in;                                           
      count++;                                  
    } 
    double avg= sum/count;                       
    System.out.println("The average is " +avg); 
  }                                                     
}

Input: 5 4 3 0 6 4 3

In particular I don't have any errors, I did have a error which said: incomparable types: boolean and int. But I fixed it, my issue now is that the average should be 4 instead of 5. I'm wondering where the error is in this, I have tried rearranging it so my average comes out to 4 , but then I often end up with the same error as above.

Its because you are adding only the first number multiple times and not reassigning in with next scanned double value — Harshavardhan Konakanchi
– Harshavardhan Konakanchi, Commented Jun 3, 2016 at 3:10
double in = scan.nextDouble(); while (scan.nextDouble()!= 0){ Since Your are not reassigning The in is 5 and condition checks for next double so for input 5 4 3 0 6 4 3 here is the value that gets added for corresponding input in bracket 5 + 5(4) + 5(3) + 5(6) + 5(4) + 5(3) so its 30/6 hence your are getting 5. — Ankur Anand
– Ankur Anand, Commented Jun 3, 2016 at 3:35

mashuai · Accepted Answer · 2016-06-03 03:14:04Z

1

import java.util.Scanner;
public class Unit2Err2{
public static void main( String[] args ){
    Scanner scan = new Scanner(System.in);
    double sum = 0;
    double count = 0;
    double in ;
    while ( (in = scan.nextDouble())!= 0){
        sum = sum + in;
        count++;
    }
    double avg= sum/count;
    System.out.println("The average is " +avg);
  }
}

when you first use nextDouble here double in = scan.nextDouble(); it has read a value from the terminal.

answered Jun 3, 2016 at 3:14

mashuai

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Comments

Jean Logeart · Accepted Answer · 2016-06-03 03:06:13Z

0

You need to re-assign in at each iteration:

while ((in = scan.nextDouble()) != 0){                                           
    sum += in;                                           
    count++;                                  
}

answered Jun 3, 2016 at 3:06

Jean Logeart

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Comments

LiveNLearn · Accepted Answer · 2016-06-03 03:16:44Z

0

The program stops and waits for input when it sees the "scan.nextDouble()" statement. Having two in a row is going to read both 5 and 4 without doing anything with the values.

The current code assigns the first input of 5 to the variable in. After that, in is never assigned the value. So 5 is being added each loop iteration.

answered Jun 3, 2016 at 3:16

LiveNLearn

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