public class Solution {
    public String joinWithSeparator(String[] arr, String separator) {
        StringBuilder result = new StringBuilder();
        
        if(arr.length == 0){
            return "";
        }


        for(int i = 0 ; i < arr.length ; i++){
            result.append(arr[i]);
            if(i != arr.length-1){
                result.append(separator);
            }
        }
        return result.toString();
    }
}