2 Hour Calculator (March 14th 2012: Pi Day)

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

public class Main {

    //Frame constructs
    public static JFrame frame;
    public static JPanel mainPanel;
    public static JPanel numbersPanel;
    public static JPanel buttonPanel;
    public static JTextArea output;
    public static JTextArea input;

    //numerical buttons
    public static JButton one;
    public static JButton two;
    public static JButton three;
    public static JButton four;
    public static JButton five;
    public static JButton six;
    public static JButton seven;
    public static JButton eight;
    public static JButton nine;
    public static JButton zero;

    //operator buttons
    public static JButton add;
    public static JButton subtract;
    public static JButton multiply;
    public static JButton divide;
    public static JButton clear;
    public static JButton clearAll;
    public static JButton decimal;

    //Action listener
    public static ActionListener buttonListener;

    //Doubles for storing math
    public static double numOne = 0;
    public static double numTwo = 0;

    public static void main(String[] args){

        //initialize all the components
        Initialize();
        //set up the GUI
        GUI();
        //update the button presses and do the math
        Update();

    }

    public static void Initialize(){

        //simple inits for frame, panels and text fields
        frame = new JFrame("Calculator");

        mainPanel = new JPanel();
        numbersPanel = new JPanel();
        buttonPanel = new JPanel();

        output = new JTextArea();
        input = new JTextArea();

        frame.setSize(300,380);
        frame.setResizable(false);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        mainPanel.setSize(300,380);
        numbersPanel.setPreferredSize(new Dimension(280,50));
        buttonPanel.setPreferredSize(new Dimension(290,380));

        output.setPreferredSize(new Dimension(280,20));
        output.setEditable(false);

        input.setPreferredSize(new Dimension(280,20));
        input.setEditable(false);

        //universal dimension to make it easier to change later
        Dimension buttonDimension = new Dimension(65,50);

        //set up dimensions for buttons
        //numerical buttons
        one = new JButton("1");
        one.setPreferredSize(buttonDimension);
        two = new JButton("2");
        two.setPreferredSize(buttonDimension);
        three = new JButton("3");
        three.setPreferredSize(buttonDimension);
        four = new JButton("4");
        four.setPreferredSize(buttonDimension);
        five = new JButton("5");
        five.setPreferredSize(buttonDimension);
        six = new JButton("6");
        six.setPreferredSize(buttonDimension);
        seven = new JButton("7");
        seven.setPreferredSize(buttonDimension);
        eight = new JButton("8");
        eight.setPreferredSize(buttonDimension);
        nine = new JButton("9");
        nine.setPreferredSize(buttonDimension);
        zero = new JButton("0");
        zero.setPreferredSize(buttonDimension);

        //operator buttons
        add = new JButton("+");
        add.setPreferredSize(buttonDimension);
        subtract = new JButton("-");
        subtract.setPreferredSize(buttonDimension);
        multiply = new JButton("x");
        multiply.setPreferredSize(buttonDimension);
        divide = new JButton("\\");
        divide.setPreferredSize(buttonDimension);
        clear = new JButton("C");
        clear.setPreferredSize(buttonDimension);
        clearAll = new JButton("Clear All");
        clearAll.setPreferredSize(new Dimension(100,50));
        decimal = new JButton(".");
        decimal.setPreferredSize(buttonDimension);
    }

    public static void GUI(){

        //add everything to the appropriate frame/panel
        frame.add(mainPanel);

        mainPanel.add(numbersPanel);
        mainPanel.add(buttonPanel);

        numbersPanel.add(output);
        numbersPanel.add(input);

        buttonPanel.add(one);
        buttonPanel.add(two);
        buttonPanel.add(three);
        buttonPanel.add(add);

        buttonPanel.add(four);
        buttonPanel.add(five);
        buttonPanel.add(six);
        buttonPanel.add(subtract);

        buttonPanel.add(seven);
        buttonPanel.add(eight);
        buttonPanel.add(nine);
        buttonPanel.add(multiply);
        buttonPanel.add(zero);

        buttonPanel.add(divide);
        buttonPanel.add(decimal);
        buttonPanel.add(clear);
        buttonPanel.add(clearAll);

        //make sure it's all visible
        frame.setVisible(true);
    }

    public static void Update(){

        //the action listener to control all the buttons
        buttonListener = new ActionListener(){
            public void actionPerformed(ActionEvent e) {

                //input for numerical buttons
                if(e.getSource().equals(one))
                    input.append("1");
                if(e.getSource().equals(two))
                    input.append("2");
                if(e.getSource().equals(three))
                    input.append("3");
                if(e.getSource().equals(four))
                    input.append("4");
                if(e.getSource().equals(five))
                    input.append("5");
                if(e.getSource().equals(six))
                    input.append("6");
                if(e.getSource().equals(seven))
                    input.append("7");
                if(e.getSource().equals(eight))
                    input.append("8");
                if(e.getSource().equals(nine))
                    input.append("9");
                if(e.getSource().equals(zero))
                    input.append("0");

                //for adding decimals
                if(e.getSource().equals(decimal))
                    input.append(".");

                //for inputting math operators
                //ADDING
                if(e.getSource().equals(add)){
                    //don't deal with empty strings
                    if(input.getText().equals(""))
                        numOne = 0;
                    else
                        numOne = Double.parseDouble(input.getText());

                    numTwo += numOne;

                    //clear the input
                    input.setText("");

                    //display the sum
                    output.setText("" + numTwo);
                }

                //SUBTRACTING
                if(e.getSource().equals(subtract)){
                    //don't deal with empty strings
                    if(input.getText().equals(""))
                        numOne = 0;
                    else
                        numOne = Double.parseDouble(input.getText());

                    numTwo -= numOne;

                    //clear the input
                    input.setText("");

                    //display difference
                    output.setText("" + numTwo);
                }

                //MULTIPLYING
                if(e.getSource().equals(multiply)){
                    //don't deal with empty strings
                    if(input.getText().equals(""))
                        numOne = 0;
                    else
                        numOne = Double.parseDouble(input.getText());

                    numTwo *= numOne;

                    //clear the input
                    input.setText("");

                    //display product
                    output.setText("" + numTwo);
                }

                //DIVIDING
                if(e.getSource().equals(divide)){
                    //don't deal with empty strings
                    if(input.getText().equals(""))
                        numOne = 0;
                    else
                        numOne = Double.parseDouble(input.getText());

                    numTwo /= numOne;

                    //clear the input
                    input.setText("");

                    //display the quotient
                    output.setText("" + numTwo);
                }

                //clear the input
                if(e.getSource().equals(clear)){
                    //clear text field
                    input.setText("");

                    //clear number in memory
                    numOne = 0;
                }

                //clear the whole calculator
                if(e.getSource().equals(clearAll)){
                    //clear the text fields
                    input.setText("");
                    output.setText("");

                    //clear the numbers in memory
                    numOne = 0;
                    numTwo = 0;
                }

            }
        };

        //add all the action listeners...
        //could probably house buttons in array and apply through that...
        one.addActionListener(buttonListener);
        two.addActionListener(buttonListener);
        three.addActionListener(buttonListener);
        four.addActionListener(buttonListener);
        five.addActionListener(buttonListener);
        six.addActionListener(buttonListener);
        seven.addActionListener(buttonListener);
        eight.addActionListener(buttonListener);
        nine.addActionListener(buttonListener);
        zero.addActionListener(buttonListener);

        add.addActionListener(buttonListener);
        subtract.addActionListener(buttonListener);
        multiply.addActionListener(buttonListener);
        divide.addActionListener(buttonListener);
        clear.addActionListener(buttonListener);
        clearAll.addActionListener(buttonListener);
        decimal.addActionListener(buttonListener);
    }

}