gistfile1.txt

public String format(List<String> list){
    boolean isFirst = true;

		StringBuilder sb = new StringBuilder();
		for(String entry : list) {
		    if (isFirst) {
		        isFirst = false;
		    } else {
		        sb.append(",");
		    }
		
			sb.append(entry);
		}
		return sb.toString();
	}