Main.java

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

class Main implements ActionListener {

    JFrame frame;
    JTextField textField;
    JButton[] numberButton = new JButton[10];
    JButton[] functionButton = new JButton[13];
    JButton addButton, subButton, mulButton, divButton;
    JButton decButton, equButton, backButton, clrButton, negButton;
    JButton expButton, factButton, modButton, squButton;
    JPanel panel;

    Font myFont = new Font("Ink Free", Font.BOLD, 30);

    double num1 = 0, num2 = 0, result = 0;
    char operator;

    Main() {

        frame = new JFrame("Krodin's Calculator");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(600, 600);
        frame.setLayout(null);
        frame.setBackground(Color.BLACK);

        textField = new JTextField();
        textField.setBounds(50, 25, 500, 50);
        textField.setFont(myFont);
        textField.setEditable(false);

        addButton = new JButton("+");
        subButton = new JButton("-");
        mulButton = new JButton("*");
        divButton = new JButton("/");
        decButton = new JButton(".");
        equButton = new JButton("=");
        backButton = new JButton("Backspace");
        clrButton = new JButton("Clear");
        negButton = new JButton("Negative");
        expButton = new JButton("Exponent");
        factButton = new JButton("Factorial");
        modButton = new JButton("Modulus");
        squButton = new JButton("Square Root");

        functionButton[0] = addButton;
        functionButton[1] = subButton;
        functionButton[2] = mulButton;
        functionButton[3] = divButton;
        functionButton[4] = decButton;
        functionButton[5] = equButton;
        functionButton[6] = backButton;
        functionButton[7] = clrButton;
        functionButton[8] = negButton;
        functionButton[9] = expButton;
        functionButton[10] = factButton;
        functionButton[11] = modButton;
        functionButton[12] = squButton;

        for (int i = 0; i < 13; i++) {

            functionButton[i].addActionListener(this);
            functionButton[i].setFont(myFont);
            functionButton[i].setFocusable(false);// sometimes made a line around button
            // when clicked so this makes
            // invisable

        } // end of for loop function buttons

        for (int i = 0; i < 10; i++) {

            numberButton[i] = new JButton(String.valueOf(i));
            numberButton[i].addActionListener(this);
            numberButton[i].setFont(myFont);
            numberButton[i].setFocusable(false);

        } // end of for loop for number buttons

        negButton.setBounds(50, 415, 163, 50);
        backButton.setBounds(216, 415, 175, 50);
        clrButton.setBounds(395, 415, 165, 50);
        expButton.setBounds(360, 101, 200, 67);
        factButton.setBounds(360, 178, 200, 67);
        modButton.setBounds(360, 255, 200, 67);
        squButton.setBounds(360, 332, 200, 67);

        panel = new JPanel();
        panel.setBounds(50, 100, 300, 300);
        panel.setLayout(new GridLayout(4, 4, 10, 10));
        panel.setBackground(Color.GRAY);// color demonstrates where the grid is

        panel.add(numberButton[1]);
        panel.add(numberButton[2]);
        panel.add(numberButton[3]);
        panel.add(addButton);
        panel.add(numberButton[4]);
        panel.add(numberButton[5]);
        panel.add(numberButton[6]);
        panel.add(subButton);
        panel.add(numberButton[7]);
        panel.add(numberButton[8]);
        panel.add(numberButton[9]);
        panel.add(mulButton);
        panel.add(decButton);
        panel.add(numberButton[0]);
        panel.add(equButton);
        panel.add(divButton);

        frame.add(panel);
        frame.add(negButton);
        frame.add(backButton);
        frame.add(clrButton);
        frame.add(expButton);
        frame.add(factButton);
        frame.add(modButton);
        frame.add(squButton);
        frame.add(textField);
        frame.setVisible(true);
        frame.setResizable(false);
        frame.setLocationRelativeTo(null);

    }// end of constructor

    public static void main(String[] args) {

        Main calculator = new Main();

    }// end of main

    static double factorial(double n) {

        if (n == 0)

            return 1;

        return n * factorial(n - 1);

    }// function to find factorial of given number

    public void actionPerformed(ActionEvent e) {

        for (int i = 0; i < 10; i++) {

            if (e.getSource() == numberButton[i]) {

                textField.setText(textField.getText().concat(String.valueOf(i)));

            } // end of if number button actioned

        } // end of for loop for number buttons

        if (e.getSource() == decButton) {

            textField.setText(textField.getText().concat(String.valueOf(".")));

        } // end of decimal button

        if (e.getSource() == addButton) {

            num1 = Double.parseDouble(textField.getText());
            operator = '+';
            textField.setText("");

        } // end of addition button

        if (e.getSource() == subButton) {

            num1 = Double.parseDouble(textField.getText());
            operator = '-';
            textField.setText("");

        } // end of subtraction button

        if (e.getSource() == mulButton) {

            num1 = Double.parseDouble(textField.getText());
            operator = '*';
            textField.setText("");

        } // end of multiplication button

        if (e.getSource() == divButton) {

            num1 = Double.parseDouble(textField.getText());
            operator = '/';
            textField.setText("");

        } // end of division button

        if (e.getSource() == expButton) {

            num1 = Double.parseDouble(textField.getText());
            operator = '^';
            textField.setText("");

        } // end of exponent button

        if (e.getSource() == factButton) {

            num1 = Double.parseDouble(textField.getText());
            result = factorial(num1);

        } // end of factorial button

        if (e.getSource() == modButton) {

            num1 = Double.parseDouble(textField.getText());
            operator = 'm';
            textField.setText("");

        }

        if (e.getSource() == squButton) {

            num1 = Double.parseDouble(textField.getText());
            result = Math.sqrt(num1);

        } // end of modulus button

        if (e.getSource() == equButton) {

            num2 = Double.parseDouble(textField.getText());

            switch (operator) {

                case '+':
                    result = num1 + num2;
                    break;
                case '-':
                    result = num1 - num2;
                    break;
                case '*':
                    result = num1 * num2;
                    break;
                case '/':
                    result = num1 / num2;
                    break;
                case '^':
                    result = Math.pow(num1, num2);
                    break;
                case 'm':
                    result = num1 % num2;
                    break;

            }// end of switch

            textField.setText(String.valueOf(result));
            num1 = result;

        } // end of equal button switch statement

        if (e.getSource() == clrButton) {

            textField.setText("");

        } // end of clear button

        if (e.getSource() == backButton) {

            String string = textField.getText();
            textField.setText("");

            for (int i = 0; i < string.length() - 1; i++) {

                textField.setText(textField.getText() + string.charAt(i));

            }

        } // end of back button

        if (e.getSource() == negButton) {

            double temp = Double.parseDouble(textField.getText());
            temp *= -1;
            textField.setText(String.valueOf(temp));

        } // end of negative button

    }// end of action performed

}// end of class