Java Calculator

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;


public class Calculator {

    private JFrame frame = new JFrame("Calculator");
    private JTextArea txtScreen = new JTextArea();
    private JLabel lblCredit = new JLabel("Created by Ben Bollinger");


    //Calculation Variables:
    String strNum1 = "";
    String strNum2 = "";
    String[] statement;
    double num1 = 0;
    double num2 = 0;
    String strTotal = "";
    double totalVal = 0;

    private JButton btnEqual = new JButton("=");

    //Number Buttons:
    private JButton btn0 = new JButton("0");
    private JButton btn1 = new JButton("1");
    private JButton btn2 = new JButton("2");
    private JButton btn3 = new JButton("3");
    private JButton btn4 = new JButton("4");
    private JButton btn5 = new JButton("5");
    private JButton btn6 = new JButton("6");
    private JButton btn7 = new JButton("7");
    private JButton btn8 = new JButton("8");
    private JButton btn9 = new JButton("9");

    //Operator Buttons:
    private JButton btnDiv = new JButton("/");
    private JButton btnMul = new JButton("*");
    private JButton btnSub = new JButton("-");
    private JButton btnAdd = new JButton("+");
    private JButton btnDec = new JButton(".");
    private JButton btnPower = new JButton("^");

    public Calculator() {
        //Frame Attributes:
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        frame.setSize(400, 560);
        frame.setResizable(false);
        frame.setLayout(null);

        //txtScreen Attributes:
        txtScreen.setSize(380, 150);
        txtScreen.setLocation(7, 15);
        txtScreen.setEditable(false);

        //lblCredit Attributes:
        lblCredit.setSize(200, 100);
        lblCredit.setLocation(12, 150);

        //btn0:
        btn0.setSize(80, 50);
        btn0.setLocation(105, 470);
        btn0.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("0");
            }
        });

        //btn1:
        btn1.setSize(80, 50);
        btn1.setLocation(10, 395);
        btn1.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("1");
            }
        });

        //btn2:
        btn2.setSize(80, 50);
        btn2.setLocation(105, 395);
        btn2.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("2");
            }
        });

        //btn3:
        btn3.setSize(80, 50);
        btn3.setLocation(200, 395);
        btn3.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("3");
            }
        });

        //btn4:
        btn4.setSize(80, 50);
        btn4.setLocation(10, 310);
        btn4.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("4");
            }
        });

        //btn5:
        btn5.setSize(80, 50);
        btn5.setLocation(105, 310);
        btn5.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("5");
            }
        });

        //btn6:
        btn6.setSize(80, 50);
        btn6.setLocation(200, 310);
        btn6.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("6");
            }
        });

        //btn7:
        btn7.setSize(80, 50);
        btn7.setLocation(10, 230);
        btn7.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("7");
            }
        });

        //btn8:
        btn8.setSize(80, 50);
        btn8.setLocation(105, 230);
        btn8.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("8");
            }
        });

        //btn9:
        btn9.setSize(80, 50);
        btn9.setLocation(200, 230);
        btn9.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("9");
            }
        });

        //btnDiv:
        btnDiv.setSize(70, 60);
        btnDiv.setLocation(310, 180);
        btnDiv.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("/");
            }
        });

        //btnMul:
        btnMul.setSize(70, 60);
        btnMul.setLocation(310, 250);
        btnMul.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("*");
            }
        });

        //btnSub
        btnSub.setSize(70, 60);
        btnSub.setLocation(310, 320);
        btnSub.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("-");
            }
        });

        //btnAdd:
        btnAdd.setSize(70, 60);
        btnAdd.setLocation(310, 390);
        btnAdd.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("+");
            }
        });

        //btnDec:
        btnDec.setSize(80, 50);
        btnDec.setLocation(200, 470);
        btnDec.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append(".");
            }
        });

        //btnPower:
        btnPower.setSize(80, 50);
        btnPower.setLocation(10, 470);
        btnPower.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                txtScreen.append("^");
            }
        });

        //btnEqual:
        btnEqual.setSize(70, 60);
        btnEqual.setLocation(310, 460);
        btnEqual.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent arg0) {
                if(txtScreen.getText().contains("+")){
                    statement = txtScreen.getText().split("\\+");

                    strNum1 = statement[0];
                    strNum2 = statement[1];

                    num1 = Double.parseDouble(strNum1);
                    num2 = Double.parseDouble(strNum2);

                    totalVal = num1 + num2;

                    strTotal = Double.toString(totalVal);

                    txtScreen.setText(strTotal);
                }
                else if(txtScreen.getText().contains("-")){
                    statement = txtScreen.getText().split("\\-");

                    strNum1 = statement[0];
                    strNum2 = statement[1];

                    num1 = Integer.parseInt(strNum1);
                    num2 = Integer.parseInt(strNum2);

                    totalVal = num1 - num2;

                    strTotal = Double.toString(totalVal);

                    txtScreen.setText(strTotal);
                }
                else if(txtScreen.getText().contains("/")){
                    statement = txtScreen.getText().split("\\/");

                    strNum1 = statement[0];
                    strNum2 = statement[1];

                    num1 = Double.parseDouble(strNum1);
                    num2 = Double.parseDouble(strNum2);

                    totalVal = num1 / num2;

                    strTotal = Double.toString(totalVal);

                    txtScreen.setText(strTotal);
                }
                else if(txtScreen.getText().contains("*")){
                    statement = txtScreen.getText().split("\\*");

                    strNum1 = statement[0];
                    strNum2 = statement[1];

                    num1 = Double.parseDouble(strNum1);
                    num2 = Double.parseDouble(strNum2);

                    totalVal = num1 * num2;

                    strTotal = Double.toString(totalVal);

                    txtScreen.setText(strTotal);
                }
                else if(txtScreen.getText().contains("^")){
                    statement = txtScreen.getText().split("\\^");

                    strNum1 = statement[0];
                    strNum2 = statement[1];

                    num1 = Double.parseDouble(strNum1);
                    num2 = Double.parseDouble(strNum2);

                    totalVal = 1;
                    for(int i = 0; i < num2; i++){
                        totalVal *= num1;
                    }

                    strTotal = Double.toString(totalVal);

                    txtScreen.setText(strTotal);
                }
            }
        });

        //Add Objects To Screen:
        frame.add(txtScreen);
        frame.add(btn0);
        frame.add(btn1);
        frame.add(btn2);
        frame.add(btn3);
        frame.add(btn4);
        frame.add(btn5);
        frame.add(btn6);
        frame.add(btn7);
        frame.add(btn8);
        frame.add(btn9);

        frame.add(lblCredit);

        frame.add(btnDiv);
        frame.add(btnMul);
        frame.add(btnSub);
        frame.add(btnAdd);
        frame.add(btnDec);
        frame.add(btnPower);

        frame.add(btnEqual);

        SwingUtilities.updateComponentTreeUI(frame);
    }

    public static void main(String[] args) {
        new Calculator();
    }

}