Question

我有两个＆＃34;文件＆＃34;。主程序和一个单独的类。

在课堂上我从数据库中获取一些数据并输出。现在我希望我的主文件抓取并输出表单（在文本框中）。但我不知道如何从主程序中获取变量或运行函数/类。

主：

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         



 NewClass ha = new NewClass();



    System.out.println(ha);
}

类别：

package kalorier;


 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;

/*
* To change this license header, choose License Headers in Project     Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

  /**
 *
 * @author anton.jeppsson
 */


 public class NewClass {



      public static void main(String[] args) throws SQLException, ClassNotFoundException {
    Class.forName("com.mysql.jdbc.Driver");
    Connection conn = null;
    String server = "localhost:3306";
    String password = "root";
    String user = "root";
    String db = "cms";
    String connectionString = "jdbc:mysql://" + server + "/" + db + "?user=" + user + "&password=" + password;
    System.out.println("Connecting with " + connectionString);
    conn = DriverManager.getConnection(connectionString);

    Statement stmt = conn.createStatement();
    ResultSet rs = stmt.executeQuery("SELECT * FROM users");
    while (rs.next()) {
       String ha = rs.getString("user_name");

     System.out.println(ha);





    }

}



}

Answer 1

可能是这样的：

按钮actionPerformed

  private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
    NewClass ha = new NewClass();
    for (String user : ha.doDatabaseStuff())
    {
      System.out.println(user);
    }
  }

<强>的NewClass

public class NewClass {

  public static void main(String[] args) {
    //Maybe do other stuff here, or is this method even necessary?
  }

  public List<String> doDatabaseStuff() {
    Class.forName("com.mysql.jdbc.Driver");
    Connection conn = null;
    String server = "localhost:3306";
    String password = "root";
    String user = "root";
    String db = "cms";
    String connectionString = "jdbc:mysql://" + server + "/" + db + "?user=" + user + "&password=" + password;
    System.out.println("Connecting with " + connectionString);
    conn = DriverManager.getConnection(connectionString);

    Statement stmt = conn.createStatement();
    ResultSet rs = stmt.executeQuery("SELECT * FROM users");

    List<String> results = new ArrayList<>();

    while (rs.next()) {
      results.add(rs.getString("user_name"));
    }

    return results;
  }
}

从单独的类运行mysql函数

1 个答案: