Question

I tried to add exception handling to my program so that when the user puts in an amount of change that is not the integer data type, the code will catch it and tell them to try again, but my try/catch isnt working. I'm not sure how to fix this problem.

JAVA code pls

package Chapter9;

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

public class GUIlab extends JFrame implements ActionListener
{
   private static final int WIDTH = 300;
   private static final int HEIGHT = 300;

   //Instance variables
   private CashRegister cashRegister = new CashRegister();
   private Dispenser candy = new Dispenser(100, 50);
   private Dispenser chips = new Dispenser(100, 65);
   private Dispenser gum = new Dispenser(75, 45);
   private Dispenser cookies = new Dispenser(100, 85);

   private JLabel headingMainL;
   private JLabel selectionL;

   private JButton exitB, candyB, chipsB, gumB, cookiesB;
   private ButtonHandler pbHandler;

   public GUIlab()
   {
       setTitle("Candy Machine"); //set the window title
       setSize(WIDTH, HEIGHT); //set the window size

       Container pane = getContentPane(); //get the container
       pane.setLayout(new GridLayout(7,1)); //set the pane layout

       pbHandler = new ButtonHandler(); //instantiate listener
       //object

       headingMainL = new JLabel("WELCOME TO SHELLY'S CANDY SHOP",
               SwingConstants.CENTER); //instantiate
       //the first label
       selectionL = new JLabel("To Make a Selection, "
               + "Click on the Product Button",
               SwingConstants.CENTER); //instantiate
       //the second label

       pane.add(headingMainL); //add the first label to the pane
       pane.add(selectionL); //add the second label to the pane

       candyB = new JButton("Candy"); //instantiate the candy
       //button
       candyB.addActionListener(pbHandler); //register the
       //listener to the
       //candy button
       chipsB = new JButton("Chips"); //instantiate the chips
       //button
       chipsB.addActionListener(pbHandler); //register the
       //listener to the
       //chips button
       gumB = new JButton("Gum"); //instantiate the gum button
       gumB.addActionListener(pbHandler); //register the listener
       //to the gum button

       cookiesB = new JButton("Cookies"); //instantiate the
       //cookies button
       cookiesB.addActionListener(pbHandler); //register the
       //listener to the cookies button

       exitB = new JButton("Exit"); //instantiate the exit button
       exitB.addActionListener(pbHandler); //register the listener
       //to the exit button

       pane.add(candyB); //add the candy button to the pane
       pane.add(chipsB); //add the chips button to the pane
       pane.add(gumB); //add the gum button to the pane
       pane.add(cookiesB); //add the cookies button to the pane
       pane.add(exitB); //add the exit button to the pane

       setVisible(true); //show the window and its contents
       setDefaultCloseOperation(EXIT_ON_CLOSE);

   } //end constructor

   //class to handle button events
   private class ButtonHandler implements ActionListener
   {
       public void actionPerformed (ActionEvent e)
       {
           if (e.getActionCommand().equals("Exit"))
               System.exit(0);
           else if (e.getActionCommand().equals("Candy"))
               sellProduct(candy, "Candy");
           else if (e.getActionCommand().equals("Chips"))
               sellProduct(chips, "Chips");
           else if (e.getActionCommand().equals("Gum"))
               sellProduct(gum, "Gum");
           else if (e.getActionCommand().equals("Cookies"))
               sellProduct(cookies, "Cookies");
       }
   }

   //Method to sell a product
   private void sellProduct(Dispenser product, String productName)
   {
       int coinsInserted = 0;
       int price;
       int coinsRequired;
       String str;
       int check = 0;

       if (product.getCount() > 0)
       {
           price = product.getCost();
           coinsRequired = price - coinsInserted;

           while (coinsRequired > 0)
           { try {
               str = JOptionPane.showInputDialog("To buy "
                       + productName
                       + " please insert "
                       + coinsRequired + " cents");
               coinsInserted = coinsInserted
                       + Integer.parseInt(str);
               coinsRequired = price - coinsInserted;
           }catch (NumberFormatException e) { JOptionPane.showMessageDialog(null,"We accept on cents(integers)", "Sorry",
                   JOptionPane.PLAIN_MESSAGE); check = -1;
                   coinsRequired = 0;
           }
           }
if (check != -1) {
           cashRegister.acceptMoney(price);
           product.makeSale();

           if (price-coinsInserted==0)
               JOptionPane.showMessageDialog(null,"Please pick up your "
                       + productName + " and enjoy",
                       "Thank you, Come again!",
                       JOptionPane.PLAIN_MESSAGE);
           else
               JOptionPane.showMessageDialog(null,"Please pick up your "
                       + productName + " and your change (" + (coinsInserted-price) + " cents) and enjoy",
                       "Thank you, Come again!",
                       JOptionPane.PLAIN_MESSAGE);
       }}
  
       else if (check != -1)//dispenser is empty
           JOptionPane.showMessageDialog(null,"Sorry "
                   + productName
                   + " is sold out\n" +
                   "Make another selection",
                   "Thank you, Come again!",
                   JOptionPane.PLAIN_MESSAGE);
   }//end sellProduct

   public static void main(String[] args)
   {
       GUIlab candyShop = new GUIlab();

   }

   @Override
   public void actionPerformed(ActionEvent e) {
       // TODO Auto-generated method stub

   }
}

Answer 1

package test;

import javax.swing.*;

public class Test{

public static void main(String []args){
int coinsRequired=100;

while (coinsRequired > 0)
{ try {
String str = JOptionPane.showInputDialog("To buy "
+ " Prod 1"
+ " please insert "
+ coinsRequired+ " cents");
int coinsInserted = Integer.parseInt(str);
coinsRequired = coinsRequired - coinsInserted;
}catch (NumberFormatException e) {

JOptionPane.showMessageDialog(null,"We accept on cents(integers)", "Sorry",JOptionPane.PLAIN_MESSAGE);

}
catch (Exception e) {

JOptionPane.showMessageDialog(null,e, "Sorry",JOptionPane.PLAIN_MESSAGE);

}
}
}
}

OUTPUT:

Input To buy Prod 1 please insert 100 cents 45,78 OK || Cancel

Sorry We accept on cents(integers) OK

Input To buy Prod 1 please insert 100 cents 660 OK Cancel

Input To buy Prod 1 please insert 34 cents 34 OK Cancel

The statements work perfectly fine.

1)It better to include a catch(Exception e) to know whether another exception has occurred

2)By setting coinsRequired =0 in catch statement it discards the while loop.

If Dispenser and CashRegister class code are provided could be of better help in understanding the exact error.