更灵活的使用PrepareStatement接口

public viod findResultSet(String sql, Object[] paras) {
   //....
   PrepareStatement pstat = conn.preparement(sql);

   //ParamentMetaData pmd = pstat.getParamenterMetaData();
   //int count = pmd.getParamenterCount();

   // String sql = "select name from user where name=? and password=?";
   for (int i = 0; i < paras.length; i++)
       //初始化sql里的占位符如：pstat.setString(1, "name"); pstat.setString(2, "password");
       pstat.setObject(i+1, paras[i]);

   pstat.executeQuery();
   //...
}

调用处1：
String sql = "select name from user where name=? and password=?";
Object[] paras = new Object[]{"lisi", "123"};
findResultSet(sql, paras);

调用处2：
String sql = "select name, password, address from user where id > ? and name=? and password=?";
Object[] paras = new Object[]{1, "lisi", "123"}; //分别对应三个问号的内容
findResultSet(sql, paras);

不需要修改函数的具体代码。
可以根据不同的参数实现了查询不同的记录！！增加了灵活性。