Thread: Simple problem...

First of all, after each if statement, since there's no bracket..it only executes the line right after it.

Second...this problem could likely be on your pricing perhaps. Nothing in the code you've posted seems to cause that error that I can find.

However, would it hurt if you had it set the message field to the credit...even if it's not equal to the lowest amount? I mean...all vending machines show the credit.

Also, you don't have to have the water button invisible till it reaches a certain amount. You could just have it not enabled.

WaterButton.setEnabled(false);

If you posted the entire code...things might be a bit clearer.

It could be for all I know that it's incrementing but not telling you that it is.

Try putting printlines after every time you increase the credit to see what it's value actually is.

public void actionPerformed(ActionEvent e)  {
        Object source = e.getSource();
        if (source == depositNickelButton) {
            v.credit += 0.05;
System.out.println(v.credit);
            if (v.credit >= v.price)
{
                setButtonEnabled(true);
            messageField.setText(cf.format(v.credit));
System.out.println(v.credit);
}
            if (v.credit >= v.price2)
{
                setSlot6Enabled(true);
            messageField.setText(cf.format(v.credit));
System.out.println(v.credit);
}
            if (v.credit >= v.price3)
{
                setSlot5Enabled(true);
            messageField.setText(cf.format(v.credit));
System.out.println(v.credit);
}
        }
       if (source == depositDimeButton) {
            v.credit += 0.10;
System.out.println(v.credit);
 
            if (v.credit >= v.price)
{
                setButtonEnabled(true);
System.out.println(v.credit);
            messageField.setText(cf.format(v.credit));
System.out.println(v.credit);
}
            if (v.credit >= v.price2)
{
System.out.println(v.credit);
                setSlot6Enabled(true);
            messageField.setText(cf.format(v.credit));
System.out.println(v.credit);
}
            if (v.credit >= v.price3)
System.out.println(v.credit);
                setSlot5Enabled(true);
            messageField.setText(cf.format(v.credit));
System.out.println(v.credit);
 
        }

I was thinking it had something to do with that too so that was among the first things i tried to use, and it didn't work. (it still waits until I hit $1.00 then displays the "Water" button, when it should display at $.90) I think I may have an error in this section:

    public boolean orderBeverage(int slot)	{
        if (credit < price)
            return false;
 
        Beverage b = stock[slot];
        if (b.quantity <= 0)
            return false;
        if (slot == 5){
				credit = credit - price3;
				return true;
		}
		if (slot == 6){
			credit = credit - price2;
			return true;
		}
 
        b.quantity--;
        credit = credit - price;
        return true;
 
    }	// end orderBevarage METHOD

but to uncomplicate things, here is all the coding:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.*;
 
public class VendingMachineApplet extends JApplet	{
 
    public void init()	{
        JPanel panel = new VendingMachinePanel();
        this.add(panel);
        setSize(470,350);
 
    }	// end init METHOD
}	// end VendingMachineApplet CLASS
 
class VendingMachinePanel extends JPanel implements ActionListener	{
 
    VendingMachine v = new VendingMachine(1.30, 1.10, 0.90);
	private JLabel depositLabel,
				   spaceLabel,
				   slot0Label,
				   slot1Label,
				   slot2Label,
				   slot3Label,
				   slot4Label,
				   slot5Label,
				   slot6Label,
				   slot7Label,
				   msgLabel;
    private JTextField messageField;
    private JButton depositQuarterButton,
                    depositDollarButton,
                    depositNickelButton,
                    depositDimeButton,
                    refundButton,
                    slot0Button,
                    slot1Button,
                    slot2Button,
                    slot3Button,
                    slot4Button,
                    slot5Button,
                    slot6Button,
                    slot7Button;
 
    NumberFormat cf = NumberFormat.getCurrencyInstance();
 
    public VendingMachinePanel()	{
        // set the layout mode for the panel
        setLayout(new GridBagLayout());
 
        // load the vending machine
        v.load(0, new Beverage("Pepsi", v.CAPACITY));
        v.load(1, new Beverage("Diet Pepsi", v.CAPACITY));
        v.load(2, new Beverage("Mountain Dew", v.CAPACITY));
        v.load(3, new Beverage("Dr. Pepper", v.CAPACITY));
        v.load(4, new Beverage("Root Beer", v.CAPACITY));
        v.load(5, new Beverage("Water", v.CAPACITY));
        v.load(6, new Beverage("Lemonade", v.CAPACITY));
        v.load(7, new Beverage("Seven-Up", v.CAPACITY));
		//deposit nickel button
		depositNickelButton = new JButton("Nickel");
		setWidth(depositNickelButton, 100);
		depositNickelButton.addActionListener(this);
		this.add(depositNickelButton, getConstraints(0,0,1,1, GridBagConstraints.NORTH));
		 //deposit dime button
		depositDimeButton = new JButton("Dime");
		setWidth(depositDimeButton, 100);
		depositDimeButton.addActionListener(this);
		this.add(depositDimeButton, getConstraints(0,1,1,1, GridBagConstraints.WEST));
 
        //deposit quarter button
        depositQuarterButton = new JButton("Quarter");
        setWidth(depositQuarterButton, 100);
        depositQuarterButton.addActionListener(this);
        this.add(depositQuarterButton, getConstraints(0,2,1,1, GridBagConstraints.WEST));
 
        //deposit dollar button
        depositDollarButton = new JButton("Dollar");
        setWidth(depositDollarButton, 100);
        depositDollarButton.addActionListener(this);
        this.add(depositDollarButton, getConstraints(0,3,1,1, GridBagConstraints.WEST));
 
		//deposited label
		depositLabel = new JLabel("      Deposited");
		this.add(depositLabel, getConstraints(0,4,1,1, GridBagConstraints.WEST));
        // message field
        messageField = new JTextField(6);
        messageField.setEditable(false);
        this.add(messageField, getConstraints(0,5,1,1, GridBagConstraints.CENTER));
 
        //refund button
        refundButton = new JButton("Refund");
        setWidth(refundButton, 100);
        refundButton.addActionListener(this);
        this.add(refundButton, getConstraints(0,6,1,1, GridBagConstraints.WEST));
 
        //slot 0 button
        slot0Button = new JButton(v.getName(0));
        setWidth(slot0Button, 120);
        slot0Button.addActionListener(this);
        this.add(slot0Button, getConstraints(2,0,1,1, GridBagConstraints.CENTER));
 
		slot0Label = new JLabel("$1.30");
		this.add(slot0Label, getConstraints(4,0,1,1, GridBagConstraints.EAST));
 
        //slot 1 button
        slot1Button = new JButton(v.getName(1));
        setWidth(slot1Button, 120);
        slot1Button.addActionListener(this);
        this.add(slot1Button, getConstraints(2,1,1,1, GridBagConstraints.CENTER));
 
		//slot 1 label
		slot0Label = new JLabel("$1.30");
		this.add(slot0Label, getConstraints(4,1,1,1, GridBagConstraints.EAST));
 
        //slot 2 button
        slot2Button = new JButton(v.getName(2));
        setWidth(slot2Button, 120);
        slot2Button.addActionListener(this);
        this.add(slot2Button, getConstraints(2,2,1,1, GridBagConstraints.CENTER));
 
		//slot 2 label
		slot0Label = new JLabel("$1.30");
		this.add(slot0Label, getConstraints(4,2,1,1, GridBagConstraints.EAST));
 
        //slot 3 button
        slot3Button = new JButton(v.getName(3));
        setWidth(slot3Button, 120);
        slot3Button.addActionListener(this);
        this.add(slot3Button, getConstraints(2,3,1,1, GridBagConstraints.CENTER));
 
		//slot 3 label
		slot0Label = new JLabel("$1.30");
		this.add(slot0Label, getConstraints(4,3,1,1, GridBagConstraints.EAST));
 
        //slot 4 button
        slot4Button = new JButton(v.getName(4));
        setWidth(slot4Button, 120);
        slot4Button.addActionListener(this);
        this.add(slot4Button, getConstraints(2,4,1,1, GridBagConstraints.CENTER));
 
		//slot 4 label
		slot0Label = new JLabel("$1.30");
		this.add(slot0Label, getConstraints(4,4,1,1, GridBagConstraints.EAST));
 
        //slot 5 button
        slot5Button = new JButton(v.getName(5));
        setWidth(slot5Button, 120);
        slot5Button.addActionListener(this);
        this.add(slot5Button, getConstraints(2,6,1,1, GridBagConstraints.CENTER));
 
		//slot 5 label
		slot0Label = new JLabel("$1.30");
		this.add(slot0Label, getConstraints(4,5,1,1, GridBagConstraints.EAST));
 
        //slot 6 button
        slot6Button = new JButton(v.getName(6));
        setWidth(slot6Button, 120);
        slot6Button.addActionListener(this);
        this.add(slot6Button, getConstraints(2,7,1,1, GridBagConstraints.CENTER));
 
		//slot 6 label
		slot0Label = new JLabel("$0.90");
		this.add(slot0Label, getConstraints(4,6,1,1, GridBagConstraints.EAST));
 
        //slot 7 button
        slot7Button = new JButton(v.getName(7));
        setWidth(slot7Button, 120);
        slot7Button.addActionListener(this);
        this.add(slot7Button, getConstraints(2,5,1,1, GridBagConstraints.CENTER));
 
		//slot 7 label
		slot0Label = new JLabel("$1.10");
		this.add(slot0Label, getConstraints(4,7,1,1, GridBagConstraints.EAST));
 
    }
 
    // a method for setting grid bag constraints
    private GridBagConstraints getConstraints(int gridx, int gridy,
    int gridwidth, int gridheight, int anchor)	    {
        GridBagConstraints c = new GridBagConstraints();
        c.insets = new Insets(5, 5, 5, 5);
        c.ipadx = 0;
        c.ipady = 0;
        c.gridx = gridx;
        c.gridy = gridy;
        c.gridwidth = gridwidth;
        c.gridheight = gridheight;
        c.anchor = anchor;
        return c;
    }	// end getConstraints METHOD
 
    // a utility method to set the button sizes
    private void setWidth(JComponent c, int width)	{
		c.setPreferredSize(new Dimension(width, 25));
    }	// end setWidth METHOD
 
    public void setButtonEnabled(boolean b)	{
        slot0Button.setEnabled(b);
        slot1Button.setEnabled(b);
        slot2Button.setEnabled(b);
        slot3Button.setEnabled(b);
        slot4Button.setEnabled(b);
        slot5Button.setEnabled(b);
        slot6Button.setEnabled(b);
        slot7Button.setEnabled(b);
    }	// end setButtonEnabled METHOD
	public void setSlot6Enabled(boolean b) {
		slot6Button.setEnabled(b);
	}
	public void setSlot5Enabled(boolean b) {
		slot5Button.setEnabled(b);
	}
    public void actionPerformed(ActionEvent e)	{
        Object source = e.getSource();
        if (source == depositNickelButton) {
			v.credit += 0.05;
			if (v.credit >= v.price)
				setButtonEnabled(true);
			messageField.setText(cf.format(v.credit));
			if (v.credit >= v.price2)
				setSlot6Enabled(true);
			messageField.setText(cf.format(v.credit));
			if (v.credit >= v.price3)
				setSlot5Enabled(true);
			messageField.setText(cf.format(v.credit));
		}
		if (source == depositDimeButton) {
			v.credit += 0.10;
			if (v.credit >= v.price)
			{
                setButtonEnabled(true);
            messageField.setText(cf.format(v.credit));
		}
        else    if (v.credit >= v.price2)
     {           setSlot6Enabled(true);
            messageField.setText(cf.format(v.credit));
}
       else     if (v.credit >= v.price3)
{
                setSlot5Enabled(true);
            messageField.setText(cf.format(v.credit));
}
 
		}
        if (source == depositQuarterButton)	{
            v.credit += 0.25;
            if (v.credit >= v.price)
                setButtonEnabled(true);
            messageField.setText(cf.format(v.credit));
			if (v.credit >= v.price2)
				setSlot6Enabled(true);
			messageField.setText(cf.format(v.credit));
			if (v.credit >= v.price3)
				setSlot5Enabled(true);
			messageField.setText(cf.format(v.credit));
        }	// end OUTER IF
        if (source == depositDollarButton)	{
            v.credit += 1.00;
            if (v.credit >= v.price)
                setButtonEnabled(true);
            messageField.setText(cf.format(v.credit));
			if (v.credit >= v.price2)
				setSlot6Enabled(true);
			messageField.setText(cf.format(v.credit));
			if (v.credit >= v.price3)
				setSlot5Enabled(true);
			messageField.setText(cf.format(v.credit));
        }	// end OUTER ELSE IF
        else if (source == slot0Button)
            order(0);
        else if (source == slot1Button)
            order(1);
        else if (source == slot2Button)
            order(2);
        else if (source == slot3Button)
            order(3);
        else if (source == slot4Button)
            order(4);
        else if (source == slot5Button)
            order(5);
        else if (source == slot6Button)
        	order(6);
        else if (source == slot7Button)
        	order(7);
        else if (source == refundButton)	{
            double refund = v.refund();
            messageField.setText(cf.format(0.0));
            JOptionPane.showMessageDialog(this, "Please take your change of " + cf.format(refund));
            setButtonEnabled(false);
        }	// end ELSE IF
    }	// end actionPerformed METHOD
 
    public void order(int slot)	    {
        if (v.orderBeverage(slot))	    {
            JOptionPane.showMessageDialog(this, "Enjoy your " + v.getName(slot));
            messageField.setText(cf.format(v.credit));
            if (v.credit < v.price)
                setButtonEnabled(false);
		}	// end OUTER IF
        else
            JOptionPane.showMessageDialog(this, v.getName(slot) + " is out of stock");
            //messageField.setText("Out of Stock");
    }	// end order METHOD
}	// end VendingMachinePanel CLASS

public class VendingMachine	{
	// the number of different types of beverages the machine can hold
    public static final int SLOTS = 8;
 
	//the number of bottles of each beverage the machine can hold
    public static final int CAPACITY = 10;
 
	// the price per beverage, set via the constructor
    public double price;
	public double price2;
	public double price3;
    // the amount the user has entered
    public double credit = 0.0;
 
    Beverage[] stock = new Beverage[SLOTS];
 
    public VendingMachine(double p, double p2, double p3)
    {	price = p;
    	price2 = p2;
    	price3 = p3;}	// end CONSTRUCTOR
 
    public void load(int slot, Beverage bev)	{
        if (slot < SLOTS)
            stock[slot] = bev;
    }	// end load METHOD
 
    public double depositMoney(double amount)	{
        credit += amount;
        return credit;
    }	// end depositMoney METHOD
 
    public boolean orderBeverage(int slot)	{
        if (credit < price)
            return false;
 
        Beverage b = stock[slot];
        if (b.quantity <= 0)
            return false;
        if (slot == 5){
				credit = credit - price3;
				return true;
		}
		if (slot == 6){
			credit = credit - price2;
			return true;
		}
 
        b.quantity--;
        credit = credit - price;
        return true;
 
    }	// end orderBevarage METHOD
 
    public double refund()	{
        double refund = credit;
        credit = 0.0;
        return refund;
    }	// end refund METHOD
 
    public String getName(int slot)	{
        if (slot < SLOTS)
            return ((Beverage)stock[slot]).name;
        else
            return "Bad slot";
    }	// end getNam METHOD
 
}	// end VendingMachine CLASS

public class Beverage	{
	public String name;
	public int quantity;
 
	public Beverage(String n, int q)	{
		name = n;
		if (q > VendingMachine.CAPACITY)
			quantity = VendingMachine.CAPACITY;
		else
			quantity = q;
	}	// end CONSTRUCTOR
}	// end Beverage CLASS

This is a problem with using floating points and truncation errors. The simplest solution is to represent the money amount using integers for cents. You can then get the dollar amounts back using money/100, and use money%100 for the cents amounts.

int money = 100 * 5 + 90; // $5.90
System.out.println("$" + money/100 + "." + money%100);

It's due to how floating points are represented. The math is rather involved, but if you're interested, see IEEE 754-2008 - Wikipedia, the free encyclopedia.

One solution is to replace everywhere it states double with integer (as I stated above). You'll need to adjust your math accordingly (increasing the value by 5 for nickels, increasing by 10 for dimes).

Something else you could try is implement the greater than to be at a half cent, since very rarely will you get an error to propagate up that much.

double sodaPrice = 0.895; // really costs 0.90
double money = 0;
for(int i = 0; i < 9; ++i)
{
    money += 0.1;
}
System.out.println("Do you have enough money? " + (sodaPrice < money));

Does it need to be (i.e. external constraint), or you don't want to change it?

It's possible to convert between the double and integer formats, though as the compiler's warning you against, you could lose precision (for money, it's almost always negligible)

double moneyD = 1.3; // $1.30
int moneyI = (int) moneyD * 100; // need an explicit cast, moneyI = 130