感觉输出哪里还是有问题哈，该怎么改啊，大家帮忙看一下哈

Question

还有点问题这个是调好的import java.sql.*;  public class jdbcyouhuo1 {  public String[] getUserName(String connString, String SQLString) throws SQLException {      Connection connection = DriverManager.getConnection(connString,"root", "root");     try {              Statement statement = connection.createStatement();         ResultSet rs = statement.executeQuery(SQLString);         int rowcount = 0;         int i = 0;          if( rs.last()) {              rowcount = rs.getRow();                            rs.beforeFirst();         }                  String[] retArray = new String[rowcount];         while (rs.next()) {             retArray[i++] = rs.getString("user_name");                      }         statement.close();         return retArray;      } catch (SQLException e ) {                   System.err.print("SQLException: ");     } finally {           }     return null; }         }  这个是还有问题的一半import java.sql.*;public class jdbcyouhua2 { public static void main(String[] agrs){  String connString = "jdbc:mysql://localhost/ace?useUnicode=true&characterEncoding=utf-8"; String SQLString = "SELECT user_name FROM users"; jdbcyouhuo1 jb1 = new jdbcyouhuo1(); try{ String[] rs = jb1.getUserName(connString, SQLString); //while(rs.next()){    System.out.println(rs.getString("user_name")); }  } catch(Exception e) {  e.printStackTrace();  } finally {     } } }是输出那里还有问题Cannot invoke getString(String) on the array type String[]

Answer 1

你的Connection变量应该在类之中,在使用ResultSet之前不可以把Statement和Connnection不应该关,你的ResultSet不应被返回而是直接把结果拿到 []string 内再返回

import java.util.Arrays;import java.lang.*;import java.sql.*;public class DatabaseConnectorTest {        private Connection connection = null;        private Statement statement = null;        public void connect(String connString) throws SQLException {                try {
                        Class.forName("org.sqlite.JDBC");
                        connection = DriverManager.getConnection(connString,"root", "root");
                } catch (SQLException e) {
                        System.err.print("connect SQLException: ");
                        System.err.println(e.getMessage());
                } catch (ClassNotFoundException e) {
                        System.err.print("ClassNotFoundException: ");
                        System.err.println(e.getMessage());
                }
        }        public String[] getUserName(String connString, String SQLString) {                ResultSet rs = null;                try {                        if(null == connection)
                                connect(connString);                        if(null == statement)
                                statement = connection.createStatement();
                        rs = statement.executeQuery(SQLString);                        int rowcount = 0;                        int i = 1;                        while(rs.next()) {
                                rowcount = i++;
                        }
                        String[] retArray = new String[rowcount];
                        i=0;
                        rs = statement.executeQuery(SQLString);                        while (rs.next()) {
                                retArray[i++] = rs.getString("user_name");
                        }                        return retArray;
                } catch (SQLException e ) {
                        System.err.print("getUserName SQLException: ");
                        System.err.println(e.getMessage());
                } finally {                        if (statement != null) {                                try { statement.close(); }                                catch(SQLException e) {
                                        System.err.print("getUserName Final SQLException: ");
                                        System.err.println(e.getMessage());
                                }
                        }
                }                return null;
        }        public static void main(String[] agrs){                String connString = "jdbc:sqlite:/tmp/test.db"; <<<< 用你自己的                String SQLString = "SELECT user_name FROM users";                DatabaseConnectorTest db = new DatabaseConnectorTest();
                String[] user_name = db.getUserName(connString, SQLString);
                System.out.println(Arrays.toString(user_name));
        }
}