package gui;

import java.awt.BorderLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.$*$;

import javax.swing.border.Border;

$//$ Defines class CalculateChange

public class CalculateChange

$\{$

$//$ Declares an object of class JFrame

JFrame jf;

$//$ Declares objects of class JPanel

JPanel jp$1,$ jp$2,$ mainP;

$//$ Declares an object of class JLabel

JLabel balanceL;

$//$ Declares an object of class JTextField

JTextField balanceT;

$//$ Declares an object of class JTextArea

JTextArea textAreaTA;

$//$ Declares an object of class JButton

JButton calculateB;

$//$ Declares an object of class JBorder

Border titleBorder;

$//$ Default constructor definition

CalculateChange$()$

$\{$

$//$ Creates a frame

jf $=$ new JFrame$("$Calculate Change from Balance"$)$;

$//$ Creates a panels

jp$1=$ new JPanel$()$;

jp$2=$ new JPanel$()$;

mainP $=$ new JPanel$()$;

$//$ Creates a label

balanceL $=$ new JLabel$("$Balance to Calculate: $")$;

$//$ Creates a text field

balanceT $=$ new JTextField$(10)$;

$//$ Creates a text area with $12$ rows and $33$ columns

textAreaTA $=$ new JTextArea$(12,33)$;

$//$ Creates a button

calculateB $=$ new JButton$("$Calculate$")$;

$//$ Creates a title border

titleBorder $=$ BorderFactory.createTitledBorder$("$Change Amounts"$)$;

$//$ Adds label, text field and buttons to panel $1$

jp$1.$add$($balanceL$)$;

jp$1.$add$($balanceT$)$;

jp$1.$add$($calculateB$)$;

$//$ Adds text area to panel $2$

jp$2.$add$($textAreaTA$)$;

$//$ Sets the title border to panel $2$

jp$2.$setBorder$($titleBorder$)$;

$//$ Sets the main panel layout to BorderLayout with $2$ rows and $1$ column

mainP.setLayout$($new BorderLayout$(2,1))$;

$//$ Adds panel $1$ to main panel at north side of main panel

mainP.add$($jp$1,$ BorderLayout.NORTH$)$;

$//$ Adds panel $2$ to main panel at center of main panel

mainP.add$($jp$2,$ BorderLayout.CENTER$)$;

$//$ Adds main panel to frame

jf$.$add$($mainP$)$;

$//$ Sets the frame other properties

jf$.$setVisible$($true$)$;

jf$.$setSize$(400,300)$;

jf$.$setLocationRelativeTo$($null$)$;

$//$ Registers action listener to calculate Button using anonymous class

calculateB.addActionListener$($new ActionListener$()$

$\{$

$//$ Overrides the actionPerformed$()$ method

public void actionPerformed$($ActionEvent ae$)$

$\{$

$//$ Checks if balance text field is empty then display error message

if$($balanceT$.$getText$().$length$()==0)$

JOptionPane.showMessageDialog$($jf$,$ "ERROR: Please enter amount."$)$;

$//$ Otherwise not empty

else

$\{$

$//$ try block begins

try

$\{$

$//$ Converts the amount entered in text field to double

double amount $=$ Double.parseDouble$($balanceT$.$getText$())$;

$//$ Checks if amount is negative then display error message

if$($amount $<=0\mathrm{.}0)$

JOptionPane.showMessageDialog$($jf$,$

"ERROR: Amount cannot be negative."$)$;

$//$ Otherwise positive

else

$\{$

$//$ Calls the method to get the changes

int $[]$result $=$ calculate$($amount$)$;

$//$ Concatenates the changes to string

String resultText $=$ "The number of $100$ dollar bills are: $"$

$+$ result$[0]$;

resultText $+="$

The number of $10$ dollar bills are: $"+$ result$[1]$;

resultText $+="$

The number of $5$ dollar bills are: $"+$ result$[2]$;

resultText $+="$

The number of quarters are: $"+$ result$[3]$;

resultText $+="$

The number of dimes are: $"+$ result$[4]$;

$//$ Sets the string result to text area

textAreaTA.setText$($resultText$)$;

$\}$

$\}$

$//$ Catch block to handle NumberFormatException

catch$($NumberFormatException ne$)$

$\{$

JOptionPane.showMessageDialog$($jf$,$ "ERROR: Invalid amount."$)$;

$\}$

$\}$

$\}//$ End of method

$\})$;$//$ End of anonymous class

$\}$

$/**$

$*$ Method to calculate change from the parameter amount

$*$ @param amount $-$ Amount whose change need to calculate

$*$ @return $-$ The array contains change for $100,10,5$ dollars, quarters and dimes

$*/$

int $[]$ calculate$($double amount$)$

$\{$

$//$ Creates array with size $5$