for循环内StringBuilder字符串拼接

public static void main(String[] args){
    String[] tempStr = {"a","b","c","d","e","f","g","h","i"};
    StringBuilder sb = new StringBuilder();
    for(String str : tempStr){
        if(!(sb.toString().length() <= 0)){
            sb.append(",");
        }
        sb.append(str);
    }
    System.out.println(sb.toString());
}