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I'm trying to create a simple grocery list GUI using JTable, before I go to the problem here is my code:

  package com.main;
  import java.awt.*;
  import javax.swing.*;
  import javax.swing.table.DefaultTableModel;
  import java.awt.event.*;

public class Whatttt extends JFrame implements ActionListener {
         JTable table;
         JScrollPane scrollpane;
         JButton addItem;
         JTextField itemName, itemAmount, itemPrice;
         DefaultTableModel model;
public Whatttt(){

  super("List n\' Go");
  setResizable(false);
  setLayout(new FlowLayout());

  itemName = new JTextField("Enter Item Name");
  add(itemName);

  itemAmount = new JTextField("Enter Item Amount");
  add(itemAmount);

  itemPrice = new JTextField("Enter Item Price");
  add(itemPrice);

  addItem = new JButton("Add Item");
  add(addItem);
  addItem.addActionListener(this);

  String [] columnnames = {"Item name", "Item Amount", "Item Price","Total Price"};
  String [] [] data = {{"test", "test", "test","test"}};

  model = new DefaultTableModel(data, columnnames);
  table = new JTable(model);
  table.setPreferredScrollableViewportSize(new Dimension(450,500));
  table.setFillsViewportHeight(true);
  
  table.getColumnModel().getColumn(0).setPreferredWidth(300);
  table.getColumnModel().getColumn(1).setPreferredWidth(100);
  table.getColumnModel().getColumn(2).setPreferredWidth(100);
  table.getColumnModel().getColumn(3).setPreferredWidth(100);


  scrollpane =new JScrollPane(table);
  add(scrollpane);


}
public static void main (String []args){
        Whatttt mainpage = new Whatttt();
        mainpage.setDefaultCloseOperation(EXIT_ON_CLOSE);
        mainpage.setSize(600,800);
        mainpage.setVisible(true);
        mainpage.setResizable(false);
    }

 public void actionPerformed(ActionEvent e) {
 if(e.getSource() == addItem){

String item = itemName.getText();
String amount= itemAmount.getText();
String price = itemPrice.getText();
String totalPrice = itemPrice.getText();

 model.insertRow(table.getRowCount(),new Object[]{item, amount, price, totalPrice});

    }
  }
  }

The problem is I want to set a specific column to accept only 1 data type, for example the column "Item amount" will only accept int values, and the "price amount" will only accept double values from the user input.

also how do you get the values from from a column? for example I want to get the value from "Item amount" and "price amount", multiply it and add it to column "Total Price. I'm still trying to learn and this serves as a practice for me, any kind of help is much appreciated.

Imaginewagons
  • 51
  • 7
  • The simplest way is to check after the user clicks the Add Item `JButton`. In the `JButton` `ActionListener`, you check to see if you can convert the item amount `String` value to an `int` (`Integer.valueOf`) and if you can convert the item price `String` to a `double` (`Double.valueOf`). One hint, save the item price as an `int` in pennies. The math works out much more accurately. – Gilbert Le Blanc May 18 '22 at 07:33
  • Save all the values in an application model, made up of one or more plain Java getter/setter classes. In your case, create an `Item` class holding the information for one item and a `GroceryList` class holding a `java.util.List` of `Item` instances. Pass an instance of the `GroceryList` class to your `JPanels`. – Gilbert Le Blanc May 18 '22 at 07:39
  • A more advanced way would be to install your own `CellEditor`s. `JSpinner` would be a good candidate, with the price column having two spinners - the rightmost for pennies – g00se May 18 '22 at 08:22
  • You need to override the `getColumnClass(...)` method of the TableModel. The table can then choose a basic editor to use for the column. Check out: https://stackoverflow.com/questions/3540661/tablemodellistener-and-multiple-column-validation/3541876#3541876 for a basic example that does what you want. This will also help with formatting of the data in each column. Note this approach will only help when editing the table directly. If you are manually adding data to the table you need to do your editing in advance as suggested by Gilbert. – camickr May 18 '22 at 14:35

0 Answers0