java，计算标准偏差。 卡在我的上一个代码中

Question

public int deviasi(){
    //sum
    int jumlah=0;
    for (int i=0; i<banyak; i++){
        jumlah = jumlah+nilai[i];
    }
    //mean
    int rata2;
    rata2=jumlah/banyak;

    //menghitung deviasi
    double deviasi = 0;
    for (int i=0;i<banyak;i++){
     deviasi += Math.pow(nilai[i] - rata2,2);
    }
    return

    Math.sqrt (deviasi/banyak);

}

i got error in my last code. it told me the problem because of different data type between deviasi and banyak. but, i've changed the data type to make them have the same data type. but the error warning still told me the problem because of different data type between deviasi and banyak. i got stuck. T_T

Answer 1

// Code returns 3.7549966711037173 public class Devs {

public static double deviasi(){

    //sum
    int jumlah= 0;
    int[] nilai = {4,7,6,3,9,12,11,12,12,15};
    int banyak = 10;


    for (int i=0; i<banyak; i++){
        jumlah += nilai[i];
    }

    //mean
    int rata2;
    rata2=jumlah/banyak;

    //menghitung deviasi
    double deviasi = 0;
    for (int i=0;i<banyak;i++){
     deviasi += Math.pow(nilai[i] - rata2,2);
    }

    return Math.sqrt (deviasi/banyak);

}

public static void main(String args[]) {


    System.out.println(deviasi());

}

}

Answer 2

Like mentioned in comments you need to work with double as variable type

public class StandDev {

  public double standardDevioation(int[] numbers){
    int count = numbers.length;
    double sum = 0.0;
    for (int i = 0; i < count; i++){
      sum += numbers[i];
    }

    double mean = sum / count;

    double sumDiff = 0.0;
    for (int i = 0; i< count; i++){
      sumDiff += Math.pow(numbers[i] - mean,2);
    }

    return Math.sqrt (sumDiff/count);
  }

  public static void main(String[] args) {
    int[] numbers =  {-5, 1, 8, 7, 2};
    StandDev standDev = new StandDev();
    System.out.println(standDev.standardDevioation(numbers));
  }
}