问获取"java.sql.SQLException: Io异常:网络适配器无法建立连接“

EN

public static void main(String[] args) {         
    try {
        DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
        Connection connection = DriverManager.getConnection(
                    "jdbc:oracle:thin:@localhost:1521:orcl", "scott", "tiger");
        Statement statement = connection.createStatement();
        ResultSet resultset = statement.executeQuery("select 'Connected' from dual");
        resultset.next();
        String s = resultset.getString(1);
        System.out.println(s);
        statement.close();
        connection.close();
    } catch (Exception e) {
        System.out.println("The exception raised is:" + e);
    }
}