import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;public class Test {    private static Connection getConn() {        String driver = "oracle.jdbc.driver.OracleDriver";        //String url = "jdbc:oracle:thin:@127.0.0.1:1521:pdbmyoracle";// 设置连接字符串        String url = "jdbc:oracle:thin:@//127.0.0.1:1521/pdbmyoracle";        String username = "abc";// 用户名        String password = "abc";// 密码        Connection conn = null; // 创建数据库连接对象        try {            Class.forName(driver);            conn = DriverManager.getConnection(url, username, password);        } catch (ClassNotFoundException e) {            e.printStackTrace();        } catch (SQLException e) {            e.printStackTrace();        }        return conn;    }    private static void query() {        Connection conn = getConn();        String sql = "select * from users";        PreparedStatement pstmt;        try {            pstmt = conn.prepareStatement(sql);            // 建立一个结果集,用来保存查询出来的结果            ResultSet rs = pstmt.executeQuery();            while (rs.next()) {                String username = rs.getString("USERNAME");                System.out.println(username);            }            rs.close();            pstmt.close();            conn.close();        } catch (SQLException e) {            e.printStackTrace();        }    }        public static void main(String[] args) {                query();    }}