为什么使用StringBuilder不能连接字符串
String content="";
int i=0;
StringBuilder Content=new StringBuilder();
for(;i<single.size();i++)
{
Ordercontent shopcar=(Ordercontent)single.get(i);
String goodsname=(String)shopcar.getGoodsname();
String num=MyTools.intToStr(shopcar.getNum());
Content.append(goodsname).append(num);
}
content=Content.toString();