Possible lossy conversion from double to int

Why am I getting the Possible lossy conversion from double to int error and how can I fix it?

public class BinSearch {
    public static void main(String [] args)
    {
        double set[] = {-3,10,5,24,45.3,10.5};
        double l = set.length;
        double i, j, first, temp;
        System.out.print("Before it can be searched, this set of numbers must be sorted: ");
        for (i = l-1; i>0; i--)
        {
            first=0;
            for(j=1; j<=i; j++)
            {
                if(set[j] < set[first]) // location of error according to compiler
                {
                    first = j;
                }
                temp = set[first];
                set[first] = set[i];
                set[i] = temp;
            }
        }
    } 
}

As you can see, I've already tried replacing int with double near the top when declaring variables but it doesn't seem to do the job.

Change all your variables used as array indices from double to int (i.e. the variables j, first, i). Array indices are integer.