Any way to fix thefollowing warning: javax.swing.JList is a raw type. References to generic type <E> should be parameterized

Question

I have this code for a shopping cart system and using javax.swing.JList is always causing problems. Is there any way to fix it by changing something? Should I write it a different way?

Here is the code. (I'm using Dr.Java, should I also use any other compiler?)

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.io.*;

public class ShoppingCartSystem extends JFrame 
{

 private JPanel sourceListPanel;
 private JPanel shoppingCartPanel;
 private JPanel buttonsPanel;

 private JList sourceList;
 private JList shoppingCart;
 private JScrollPane scrollPane;
 private JScrollPane scrollPane2;

 private JButton addButton;
 private JButton removeButton;
 private JButton checkListButton;

 private String []books;
 private double []price;
 private String []cart;
 private int cartSize;
 private double subTotal = 0.0,tax,total;

ShoppingCartSystem()
{
     setTitle("Shopping Cart System");
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     setLayout(new BorderLayout());

     books = new String[25];
     price = new double[25];
     cart = new String[25];
     cartSize =0;

     readDataFromFile();
     buildSourceListPanel();
     buildShoppingCartPanel();
     buildButtonsPanel();

    add(sourceListPanel,BorderLayout.WEST);
     add(shoppingCartPanel,BorderLayout.EAST);
     add(buttonsPanel,BorderLayout.SOUTH);
     pack();
     setVisible(true);
 }

private void readDataFromFile()
{
     try{
         DataInputStream dis = new DataInputStream(new FileInputStream("BookPrices.txt"));
         BufferedReader br = new BufferedReader(new InputStreamReader(dis));
         int i=0;
         String line;
         while((line = br.readLine()) != null){
             String []arr = line.split(", ");
             books[i] = arr[0];
             price[i++] = Double.parseDouble(arr[1]);
         }
         br.close();
         dis.close();
     }
     catch(Exception exp)
{
         System.out.println(exp.toString());
     }

 }

private void buildSourceListPanel()
{
     sourceListPanel = new JPanel();
     sourceList = new JList(books);
     sourceList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
     sourceList.setVisibleRowCount(6);       
     scrollPane = new JScrollPane(sourceList);
     sourceListPanel.add(scrollPane);
 }

private void buildShoppingCartPanel()
{
     shoppingCartPanel = new JPanel();
     shoppingCart = new JList();       
     shoppingCart.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
     shoppingCart.setVisibleRowCount(6);       
     scrollPane2 = new JScrollPane(shoppingCart);
     shoppingCartPanel.add(scrollPane2);
 }

private void buildButtonsPanel()
{
     buttonsPanel =new JPanel();
     addButton = new JButton("Add to shopping cart");
     removeButton = new JButton("Remove from shopping cart");
     checkListButton =new JButton("Check List");
     buttonsPanel.setLayout(new FlowLayout(10));
     buttonsPanel.add(addButton);
     buttonsPanel.add(removeButton);
     buttonsPanel.add(checkListButton);
     addButton.addActionListener(new ButtonListener());
     removeButton.addActionListener(new ButtonListener());
     checkListButton.addActionListener(new ButtonListener());
 }

private class ButtonListener implements ActionListener
{

    public void actionPerformed(ActionEvent ae)
{

        if(ae.getSource() == addButton)
         {               
             cart[cartSize++] = (String) sourceList.getSelectedValue();
             shoppingCart.setListData(cart);
             subTotal += price[sourceList.getSelectedIndex()];
         }
         else if(ae.getSource() == removeButton)
         {
             for(int i=0;i<books.length;i++)
                 if(shoppingCart.getSelectedValue().equals(books[i]))
                 {
                    subTotal -= price[i];
                    break;
                 }

             int selection = shoppingCart.getSelectedIndex();

            for(int i=selection; i< cart.length-1;i++)
                 cart[i] = cart[i+1];
             shoppingCart.setListData(cart);               
         }
         else
         {
             java.text.DecimalFormat df = new java.text.DecimalFormat("#.##");
             tax = subTotal * 0.06;
             total = subTotal + tax;
             StringBuffer sb = new StringBuffer();
             sb.append("Sub Total: "+df.format(subTotal)+"\n");
             sb.append("Tax: "+df.format(tax)+"\n");
             sb.append("Total: "+df.format(total)+"\n");
             JOptionPane.showMessageDialog(null, sb);
         }
     }
 }

 public static void main(String []args)
{
     new ShoppingCartSystem();
 }

}

Answer 1

Yes. You appear to want to contain String(s), so you could declare your JList with the String Generic Type. Something like

private JList<String> sourceList;
private JList<String> shoppingCart;

and, then initialize them like

sourceList = new JList<>();
// ...
shoppingCart = new JList<>();

or, you could declare and initialize at the same time

private JList<String> sourceList = new JList<>();
private JList<String> shoppingCart = new JList<>();