java 数组转换成字符串 类似 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(); }