从 List<class> 获取数据并将其放入 String 对象

Question

我正在制作一个 java 简单的应用程序，以便更好地学习代码，结合一些 intellji 上的 gui。

我已经有一个主页，我只是想制作一个弹出表，其中包含我产品上的所有数据，这是我的 tableView 代码：

public class ProductTable extends JFrame
{
    private Model.product product;
    private List<product> list;

    public ProductTable() {
        list = product.ProductList();

        // headers for the table
        String[] columns = {"Product Name",
                "Quantity",
                "Expiration day",
                "Need fridge"};
        Object[][] data = new Object[][] {
        };

        // create table with data
        JTable table = new JTable(data, columns);

        // add the table to the frame
        this.add(new JScrollPane(table));
        this.setTitle("ProductList");
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.pack();
        this.setVisible(true);
    }

    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new ProductTable();
            }
        });
    }
}   

在Product 课程中我有：

product.name = String
product.quantity = int
Product.Expiration_day = String
product.fridge = boolean

我想加载到字符串对象中

Data={ {product.name, product.quantity, Product.Expiration_day, Product.fridge} ,{.....,....,....,...}{..............}};

直到我把所有的数据都放进去，现在我知道如何知道大小了，但是我需要将它一个一个地加载到数据对象中，请有人指导一下吗？！

我的产品代码：

package Model;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class product
{
    private String product_name;
    private Integer product_quantity;
    private String experation_day;
    private boolean fridge = false;
    private boolean matched= false;
    private Connection connection;

    public product()
    {
        this.product_name = "";
        this.product_quantity = 0;
        this.experation_day = "";
    }

    public product(String product_name, Integer product_quantity, String experation_day) {
        this.product_name = product_name;
        this.product_quantity = product_quantity;
        this.experation_day = experation_day;
    }

    public Integer getProduct_quantity() {
        return product_quantity;
    }

    public String getExperation_day() {
        return experation_day;
    }

    public String getProduct_name()
    {
        return product_name;
    }

    public void setProduct_quantity(Integer product_quantity) {
        this.product_quantity = product_quantity;
    }

    public void setExperation_day(String experation_day) {
        this.experation_day = experation_day;
    }

    public void setProduct_name(String product_name)
    {
        this.product_name = product_name;
    }

    public List<product> ProductList() {

        String windownsUserName = System.getProperty("user.name");
        try
        {
            System.out.println("Connecting to a selected database...");
            Connection connection = DriverManager.getConnection("jdbc:sqlite:C:\\Users\\"+windownsUserName+"\\IdeaProjects\\Software-engineer-final-project\\untitled\\src\\DButills\\account.db");
            System.out.println("Connected database successfully...");
            String sqlQuery = "SELECT product_name, product_amount, product_expration_date FROM products";
            PreparedStatement ps = connection.prepareStatement(sqlQuery);
            ResultSet rs = ps.executeQuery();
            {

            }
            List<product> products = new ArrayList<>();
            while (rs.next()) {
                product product = new product();
                product.setProduct_quantity(rs.getInt("product_amount"));
                product.setProduct_name(rs.getString("product_name"));
                product.setExperation_day(rs.getString("product_expration_date"));
                products.add(product);
            }
            return products;

        } catch (SQLException e) {
            System.out.println("Query failed: " + e.getMessage());
            return null;
        }
    }
}

Answer 1

'package viewer;

导入模型.product;

导入 javax.swing.*;

导入 java.awt.*;

导入 java.util.List；

公共类 ProductTable 扩展 JFrame

{ 私有 Model.product 产品；

private Container c;

private JTable table;

Object[] mdata;

private List<product> list;

String[] columns = {"Product Name", "Quantity", "Expiration day"};  //headers for the table
int i=1;

私有对象[][] 数据 = 新对象[][] { };

public ProductTable()
{
    list=product.ProductList();
   while(i<=list.size()) {

       mdata = new Object[]{list.get(i).getProduct_name(), list.get(i).getExperation_day(), list.get(i).getProduct_quantity().toString()};

       data[0][i]=mdata[0];

       data[1][i]=mdata[1];

       data[2][i]=mdata[2];

       i++;
   }

    //create table with data

    JTable table = new JTable(data, columns);

  //add the table to the frame

    this.setTitle("ProductList");

    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    setVisible(true);
}

}'

Answer 2

为什么需要 String？根据您提供的代码 - 您需要的是一个数组 Object[][]，但其中填充了值，因此只需遍历您的产品列表并填写您的 数据按正确顺序排列。

编辑：

看看这个伪代码，它应该看起来像这样：

   String[] columns = {"Product Name",
            "Quantity",
            "Expiration day",
            "Need fridge"};
   Object[][] data = new Object[list.size()][columns.length];
   int columnCounter = 0;
   for(Product product : list) {
       data[columnCounter][0] = product.getName();
       data[columnCounter][1] = product.getQuantity();
       data[columnCounter][2] = product.getExpDay();
       data[columnCounter][3] = product.getNeedFridge();
       columnCounter++;
   }