java的resultset的next_java如何两次运行Resultsetet.next()？

我有这种方法来获取一行字符串并打印它们.

另外,我必须做两次while(Resultset.next())两次.第一个是获取行数,第二个是打印字符串.但是,当该方法第一次运行Resultset.next()时,该方法将跳过第二个Resultset.next().

public static String[] gett() throws ClassNotFoundException, SQLException{

// this for get conneced to the database .......................

Class.forName("oracle.jdbc.driver.OracleDriver");

Connection conn &＃61; DriverManager.getConnection("jdbc:oracle:thin:&＃64;localhost:1521:XE","hr","111");

Statement st &＃61; conn.createStatement();

ResultSet re &＃61; st.executeQuery("select location_id from DEPARTMENTS");

// Ok , now i have the ResultSet ...

// the num_row it&＃39;s counter to get number of rows

int num_row &＃61; 0;

// this Arrar to store String values

String[] n &＃61; new String[num_row];

// this is the first ResultSet.next , and it&＃39;s work ..!

// also , this ResultSet.next work to get number on rows and store the number on &＃39;num_row&＃39;

while(re.next())

num_row&＃43;&＃43;;

// NOW , this is the secound &＃39;ResultSet.next()&＃39; , and it&＃39;s doesn&＃39;t WORK !!!!

while(re.next()) {

System.out.println(re.getString("location_id"));

}

}

问题是,第一个Resultset.next()可以正常工作,但是第二个则无法工作&＃xff01;

有人可以解释为什么吗&＃xff1f;我该如何运作呢&＃xff1f;

注意&＃xff1a;

我知道,在一个Resultset.next()中还有另一种方法可以做到这一点.

但是我想做两次;)

解决方法:

您可以将您的Statement初始化为以下内容

conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);

因此,您可以在Statement中移动光标.

现在您可以遍历它.

while(re.next())

num_row&＃43;&＃43;;

re.beforeFirst();

但这是不必要的,最佳解决方案是跳到集合的末尾并返回行

num_row &＃61; 0;

if(re.last()) {

num_row &＃61; rs.getRow();

re.beforeFirst();

}

标签&＃xff1a;oracle,jdbc,resultset,sql,java

来源&＃xff1a; https://codeday.me/bug/20191119/2035922.html