Is there a way to implement Stack to perform calculations with this code?

import java.awt.EventQueue;

import javax.swing.JFrame;

import javax.swing.JTextField;

import javax.swing.JButton;

import java.awt.Font;

import java.awt.event.ActionListener;

import java.awt.event.ActionEvent;

import javax.swing.SwingConstants;

public class Calculator {

private JFrame frame;

private JTextField textField;

double input1;

double input2;

double result;

String operation;

String answer;

/**

* Launch the application.

*/

public static void main(String[] args) {

EventQueue.invokeLater(new Runnable() {

public void run() {

try {

Calculator window = new Calculator();

window.frame.setVisible(true);

} catch (Exception e) {

e.printStackTrace();

}

}

});

}

/**

* Create the application.

*/

public Calculator() {

initialize();

}

/**

* Initialize the contents of the frame.

*/

private void initialize() {

frame = new JFrame();

frame.setBounds(100, 100, 246, 362);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.getContentPane().setLayout(null);

textField = new JTextField();

textField.setHorizontalAlignment(SwingConstants.RIGHT);

textField.setBounds(6, 6, 232, 36);

frame.getContentPane().add(textField);

textField.setColumns(10);

//Row 1

JButton btn7 = new JButton("7");

btn7.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btn7.getText();

textField.setText(input);

}

});

btn7.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btn7.setBounds(6, 44, 50, 50);

frame.getContentPane().add(btn7);

JButton btn8 = new JButton("8");

btn8.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btn8.getText();

textField.setText(input);

}

});

btn8.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btn8.setBounds(68, 44, 50, 50);

frame.getContentPane().add(btn8);

JButton btn9 = new JButton("9");

btn9.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btn9.getText();

textField.setText(input);

}

});

btn9.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btn9.setBounds(128, 44, 50, 50);

frame.getContentPane().add(btn9);

JButton btnPlus = new JButton("+");

btnPlus.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

input1 = Double.parseDouble(textField.getText());

textField.setText("");;

operation = "+";

}

});

btnPlus.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btnPlus.setBounds(188, 44, 50, 50);

frame.getContentPane().add(btnPlus);

//Row 1

//Row 2

JButton btn4 = new JButton("4");

btn4.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btn4.getText();

textField.setText(input);

}

});

btn4.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btn4.setBounds(6, 104, 50, 50);

frame.getContentPane().add(btn4);

JButton btn5 = new JButton("5");

btn5.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btn5.getText();

textField.setText(input);

}

});

btn5.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btn5.setBounds(68, 104, 50, 50);

frame.getContentPane().add(btn5);

JButton btn6 = new JButton("6");

btn6.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btn6.getText();

textField.setText(input);

}

});

btn6.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btn6.setBounds(128, 104, 50, 50);

frame.getContentPane().add(btn6);

JButton btnSub = new JButton("-");

btnSub.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

input1 = Double.parseDouble(textField.getText());

textField.setText("");;

operation = "-";

}

});

btnSub.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btnSub.setBounds(188, 104, 50, 50);

frame.getContentPane().add(btnSub);

//Row 2

//Row 3

JButton btn1 = new JButton("1");

btn1.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btn1.getText();

textField.setText(input);

}

});

btn1.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btn1.setBounds(6, 164, 50, 50);

frame.getContentPane().add(btn1);

JButton btn2 = new JButton("2");

btn2.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btn2.getText();

textField.setText(input);

}

});

btn2.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btn2.setBounds(68, 164, 50, 50);

frame.getContentPane().add(btn2);

JButton btn3 = new JButton("3");

btn3.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btn3.getText();

textField.setText(input);

}

});

btn3.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btn3.setBounds(128, 164, 50, 50);

frame.getContentPane().add(btn3);

JButton btnM = new JButton("*");

btnM.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

input1 = Double.parseDouble(textField.getText());

textField.setText("");;

operation = "*";

}

});

btnM.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btnM.setBounds(188, 164, 50, 50);

frame.getContentPane().add(btnM);

//Row 3

//Row 4

JButton btn0 = new JButton("0");

btn0.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btn0.getText();

textField.setText(input);

}

});

btn0.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btn0.setBounds(6, 224, 50, 50);

frame.getContentPane().add(btn0);

JButton btnPeriod = new JButton(".");

btnPeriod.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btnPeriod.getText();

textField.setText(input);

}

});

btnPeriod.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btnPeriod.setBounds(68, 224, 50, 50);

frame.getContentPane().add(btnPeriod);

JButton btnPM = new JButton("+/-");

btnPM.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

double pm = Double.parseDouble(String.valueOf(textField.getText()));

pm = pm*(-1);

textField.setText(String.valueOf(pm));

}

});

btnPM.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btnPM.setBounds(128, 224, 50, 50);

frame.getContentPane().add(btnPM);

JButton btnEquals = new JButton("=");

btnEquals.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String answer;

input2 = Double.parseDouble(textField.getText());

if (operation == "+") {

result = input1 + input2;

answer = String.format("%.2f",result);

textField.setText(answer);

}else if (operation == "-") {

result = input1 - input2;

answer = String.format("%.2f",result);

textField.setText(answer);

}else if (operation == "*"); {

result = input1 * input2;

answer = String.format("%.2f",result);

textField.setText(answer);

}

}

});

btnEquals.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btnEquals.setBounds(188, 224, 50, 50);

frame.getContentPane().add(btnEquals);

//Row 4

//Row 5

JButton btnDel = new JButton("?");

btnDel.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String delete = null;

if(textField.getText().length() > 0) {

StringBuilder sB = new StringBuilder(textField.getText());

sB.deleteCharAt(textField.getText().length() - 1);

delete = sB.toString();

textField.setText(delete);;

}

}

});

btnDel.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btnDel.setBounds(6, 284, 50, 50);

frame.getContentPane().add(btnDel);

JButton btnClear = new JButton("C");

btnClear.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

textField.setText(null);

}

});

btnClear.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btnClear.setBounds(68, 284, 50, 50);

frame.getContentPane().add(btnClear);

JButton btnMod = new JButton("%");

btnMod.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

input1 = Double.parseDouble(textField.getText());

textField.setText("");;

operation = "%";

}

});

btnMod.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btnMod.setBounds(128, 284, 50, 50);

frame.getContentPane().add(btnMod);

JButton btnDiv = new JButton("/");

btnDiv.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

String input = textField.getText() + btnDiv.getText();

textField.setText(input);

}

});

btnDiv.setFont(new Font("Lucida Grande", Font.PLAIN, 18));

btnDiv.setBounds(188, 284, 50, 50);

frame.getContentPane().add(btnDiv);

//Row 5

}

}