Java 數組轉換成字符串 添加逗號 類似 js array的join

public static String join( Object[] o , String flag ){
        StringBuffer str_buff = new StringBuffer();
        for(int i=0 , len=o.length ; i<len ; i++){
            str_buff.append( String.valueOf( o[i] ) );
            if(i<len-1)str_buff.append( flag );
        }
        return str_buff.toString(); 
}