Expenses calculator

Submitted by pavel7_7_7 on Friday, September 5, 2014 - 08:19.

Java swing library is a library that is used for creation of java application with Graphical User Interface (GUI). The whole project will consist of two classes: The first class will be the application class that will hold the GUI of the application:

public class Expenses extends JFrame implements ActionListener

The second class will be a class, that will represent an expense panel with the information:

class ExpensesPanel extends JPanel implements ActionListener

An expense record is represented by the following data:

//data
String name;
String data;
float cost;
int number;

These fields will be represented in this panel by the Labels:

JLabel 	nameLabel,
	dataLabel,
	costLabel,
	numberLabel;

Also, there is an option to delete an expense record by pressing a button:

//delete
JButton delete;

An array of colors is used to fill every expense panel with different color:

//array of colors for background
Color[] colors;

The constructor of this class initializes fields and sets data to the labels and adds labels to the panel:

ExpensesPanel(String _name, String _data, float _cost,int _number){
		initColors();//initializing colors for expenses
		//save data
		name = _name;
		data = _data;
		cost = _cost;
		number = _number;
		//creating labels
		nameLabel = new JLabel(name);
		dataLabel = new JLabel(data);
		costLabel = new JLabel(new Double(cost).toString());//converting double to string
		numberLabel = new JLabel(new Integer(number).toString());//converting int to string
		delete = new JButton("Delete");//a button to delete expense
		delete.addActionListener(this);//action listener for delete
		//horizontal box layout for panel
		this.setLayout(new BoxLayout(this,BoxLayout.X_AXIS));
		add(numberLabel);
		//adding glue
		add(Box.createHorizontalGlue());
		add(nameLabel);
		//adding glue
		add(Box.createHorizontalGlue());
		add(dataLabel);
		//adding glue
		add(Box.createHorizontalGlue());
		add(costLabel);
		//adding glue
		add(Box.createHorizontalGlue());
		add(delete);
	}

The array of colors is initialized with ten different colors:

/**
	 * init the array of colors
	 */
	private void initColors() {
		//initialize colors
		colors = new Color[10];
		colors[0] = Color.blue;
		colors[1] = Color.cyan;
		colors[2] = Color.darkGray;
		colors[3] = Color.green;
		colors[4] = Color.magenta;
		colors[5] = Color.orange;
		colors[6] = Color.pink;
		colors[7] = Color.yellow;
		colors[8] = Color.white;
		colors[9] = Color.red;
	}

The interaction with the main class ti send the cost of the expense is done by a public method:

public float getCost(){
	return cost;
}

The background of the panel is set in public void paintComponent(Graphics g)

public void paintComponent(Graphics g){
	//setting the color of expense according to it's number
	this.setBackground(colors[number%10]);
	super.paintComponent(g);
}

The last thing that should be implemented is the delete option:

@Override
public void actionPerformed(ActionEvent e ) {
	if(e.getSource() == delete){
		//delete from panel3
		JPanel parent = (JPanel)this.getParent();
		parent.remove(this);
		//getting the Expenses class to update stats and modify vector
		Expenses e1 = (Expenses) parent.getParent().getParent().getParent().getParent().getParent().getParent().getParent();
		if(number!=0)
			e1.allExpenses.remove(number - 1);
		else
		        e1.allExpenses.remove(0);
		for(int i = 0; i != e1.allExpenses.size();++i){
			e1.allExpenses.get(i).number = i;//setting new numbers
		}
		e1.updateStats();//update statistics
		e1.validate();//validate data
		e1.repaint();//repaint
}

Now we can implement the application class the will contain the data of all expenses. The list of all GUI elements that will display the data and the information to add expenses is represented by private fields:

//private fields
private JLabel name_label,date_label,cost_label, total_exp, average_exp;  
private JTextField name_tf,date_tf,cost_tf, total_tf, average_tf;
private JPanel panel1,panel2,panel3,panel4;
private JButton button1add, button2clear; 
JScrollPane sp;
ArrayList<ExpensesPanel> allExpenses; 	//vector to hold expenses

The constructor of this class initializes all the variables. The first step is to set size of the frame, its title and option that the from should me closed if the exit sign is pressed:

//size,title, exit	
setSize(400,400);
setTitle("Calculator");
setDefaultCloseOperation(EXIT_ON_CLOSE);

The initialization of the elements it's done by adding text to all the labels and placing them to the different panels. The data of an expense is entered in text fields and it's added by pressing

Add Expense

button:

//panel 1
		panel1 = new JPanel();	
		panel1.setLayout(new BoxLayout(panel1,BoxLayout.Y_AXIS));
		getContentPane().add(panel1);	
		//panel 2
		panel2 = new JPanel(new GridLayout(4,2));
		panel1.add(panel2);	
		// creating labels
		name_label = new JLabel("name");
		date_label = new JLabel("date");
		cost_label = new JLabel("cost");
		//creating the text fields
		name_tf = new JTextField("Name");
		date_tf = new JTextField("Date");
		cost_tf = new JTextField("Cost");
		//aligning the textfields to the right
		name_tf.setHorizontalAlignment(JTextField.RIGHT);
		date_tf.setHorizontalAlignment(JTextField.RIGHT);
		cost_tf.setHorizontalAlignment(JTextField.RIGHT);
		panel2.setMaximumSize(new Dimension(Integer.MAX_VALUE,(int)panel2.getPreferredSize().getHeight()));
		//adding labels & textfield to panel2
		//first row
		panel2.add(name_label); panel2.add(name_tf);
		//second row
		panel2.add(date_label); panel2.add(date_tf);
		//third row
		panel2.add(cost_label); panel2.add(cost_tf);
		//create button(add and clear)
		button1add = new JButton("Add Expenses");
		button2clear = new JButton("Clear Expenses");
		panel2.add(button1add);
		panel2.add(button2clear);
		//panel 3,vertical layout,scrollpane
		panel3 = new JPanel();
		panel3.setLayout(new BoxLayout(panel3,BoxLayout.Y_AXIS));
		//JTextArea ta = new JTextArea();
		sp = new JScrollPane(panel3);
		//panel3.add(sp);
		panel1.add(sp);
		//panel 4, labels total exp and ave exp, with uneditable txtfield
		panel4 = new JPanel(new GridLayout(2,2));
		panel1.add(panel4);
		total_exp = new JLabel("Total Expenses");
		average_exp = new JLabel("Average Expenses");
		average_tf = new JTextField();
		total_tf = new JTextField();
		  //disable textfields
		  average_tf.setEditable(false);
		  total_tf.setEditable(false);
		  // add new label to panel4 and txtfield
		  panel4.add(total_exp);	panel4.add(total_tf);
		  panel4.add(average_exp);  panel4.add(average_tf);
		  //set max size of panel4
		  panel4.setMaximumSize(new Dimension(Integer.MAX_VALUE,(int)panel4.getPreferredSize().getHeight()));
		  //add action listeners to buttons
		  button1add.addActionListener(this);
		  button2clear.addActionListener(this);
		  //vector for expenses
		  allExpenses = new ArrayList<ExpensesPanel>();

As you can see, there two buttons that have ActionListeners. Let's take a look on the handling of pressing

Add Expense

button and

clear Expenses

button:

@Override
	public void actionPerformed(ActionEvent e) {
		// TODO Auto-generated method stub
		//add expense
		if(e.getSource()==button1add){
			addExpense();
			updateStats();
		}
		//clear list
		if(e.getSource()==button2clear){
			clearExpense();
			updateStats();
		}
 
	}

Adding an expense operation is performed in user defined method:

private void addExpense() {
		//creating an Expense
		ExpensesPanel newExpense = new ExpensesPanel(name_tf.getText(),date_tf.getText(),Float.parseFloat(cost_tf.getText()),allExpenses.size()+1);
		allExpenses.add(newExpense);//add expense to vector
		panel3.add(newExpense);//adding new expense to pannel3
		//update the stats
		updateStats();
		panel3.validate();//repaint panel 3
		panel3.repaint();
	}

An expense is creating b getting data from the input text fields. After this, it's added to the screen and to the array of all expenses. The clearExpenses method simply removes all the data from the array and expense panel:

private void clearExpense() {
		// TODO Auto-generated method stub
		for(int i = 0; i != allExpenses.size(); ++i){
			panel3.remove(allExpenses.get(i));//remove data from vector
		}
		//repaint panel without data
		allExpenses.clear();//clear
		panel3.validate();//validate data
		panel3.repaint();//repaint panel
 
	}

The updateStats method get the total cost of all expenses, calculates average expense and displays these values in the text fields:

void updateStats(){
		float total = 0;//total sum is initially 0
		for(int i = 0; i != allExpenses.size(); ++i){
			total += allExpenses.get(i).getCost();//ading to total cost of all expenses
		}
		total_tf.setText(new Double(total).toString());//change total text field with achieved data
		average_tf.setText(new Double(total/allExpenses.size()).toString());//avg = total/number
	}

To start any java application we need to have a main method. In this case, the main method simply creates and start an object of the Expense calculator application:

public static void main(String[] args) {
		// TODO Auto-generated method stub
		Expenses my = new Expenses();//creates frame
		my.setVisible(true);//setting this frame visible
 
	}

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Expenses calculator

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