Java string compression is printing wrong string. What am I missing here?

I have a string "aaabbaaaavvvd", it should be compressed to a3b2a4v3d But when I run my code it prints out b3a2v4d3

Strangely, it starts with b instead of a

public class compression {
    public String compress(String str){
        char chararr[] = str.toCharArray();
        StringBuilder sb = new StringBuilder();
        int count=1;
        char previous = chararr[0];
        for(int i=1; i<chararr.length; i++) {
             char current = chararr[i]; 
             if(current == previous){
                 count++;
             } else {
                 sb.append(current).append(count);
                 count = 1;
             }
             previous = current;
        }
        System.out.println(sb.toString());
        return sb.toString();
    }

    public static void main(String args[]){
        compression test = new compression();
        String str = "aaabbaaaavvvd";
        test.compress(str);
    }
}