Calc project in NB, for stackOF

package calcGui;


public class GUI extends javax.swing.JFrame {

    double firstNumber;
    double secondNumber;
    String operation;

    /** Creates new form GUI */
    public GUI() {
        initComponents();
    }
    @SuppressWarnings("unchecked")
      "Generated Code spoiler thingy"

private void btn1ActionPerformed(java.awt.event.ActionEvent evt) {
    String input = txtDisplay.getText() + btn1.getText();
    txtDisplay.setText(input);
}

private void btn2ActionPerformed(java.awt.event.ActionEvent evt) {
    String input = txtDisplay.getText() + btn2.getText();
    txtDisplay.setText(input);
}

private void btn3ActionPerformed(java.awt.event.ActionEvent evt) {
    String input = txtDisplay.getText() + btn3.getText();
    txtDisplay.setText(input);
}

private void btn4ActionPerformed(java.awt.event.ActionEvent evt) {
    String input = txtDisplay.getText() + btn4.getText();
    txtDisplay.setText(input);
}

private void btn5ActionPerformed(java.awt.event.ActionEvent evt) {
    String input = txtDisplay.getText() + btn5.getText();
    txtDisplay.setText(input);
}

private void btn6ActionPerformed(java.awt.event.ActionEvent evt) {
    String input = txtDisplay.getText() + btn6.getText();
    txtDisplay.setText(input);
}

private void btn7ActionPerformed(java.awt.event.ActionEvent evt) {
    String input = txtDisplay.getText() + btn7.getText();
    txtDisplay.setText(input);
}

private void btn8ActionPerformed(java.awt.event.ActionEvent evt) {
    String input = txtDisplay.getText() + btn8.getText();
    txtDisplay.setText(input);
}

private void btn9ActionPerformed(java.awt.event.ActionEvent evt) {
    String input = txtDisplay.getText() + btn9.getText();
    txtDisplay.setText(input);
}

private void btn0ActionPerformed(java.awt.event.ActionEvent evt) {
    String input = txtDisplay.getText() + btn0.getText();
    txtDisplay.setText(input);
}

private void btnClrActionPerformed(java.awt.event.ActionEvent evt) {
    txtDisplay.setText("");
}

private void btnPtActionPerformed(java.awt.event.ActionEvent evt) {
    int count = txtDisplay.getText().length() - txtDisplay.getText().replace(".", "").length();

    if(count == 0){
        String input= txtDisplay.getText() + btnPt.getText();
        txtDisplay.setText(input);
    }
    else{

    }
}

private void btnPlusActionPerformed(java.awt.event.ActionEvent evt) {

    firstNumber = Double.parseDouble(txtDisplay.getText());
    txtDisplay.setText("");
    operation = "+";



}

private void btnMnsActionPerformed(java.awt.event.ActionEvent evt) {
    firstNumber = Double.parseDouble(txtDisplay.getText());
    txtDisplay.setText("");
    operation = "-";
}

private void btnMultiActionPerformed(java.awt.event.ActionEvent evt) {
    firstNumber = Double.parseDouble(txtDisplay.getText());
    txtDisplay.setText("");
    operation = "*";
}

private void btnDivActionPerformed(java.awt.event.ActionEvent evt) {
    firstNumber = Double.parseDouble(txtDisplay.getText());
    txtDisplay.setText("");
    operation = "/";
}

private void btnEqActionPerformed(java.awt.event.ActionEvent evt) {
    secondNumber = Double.parseDouble(txtDisplay.getText());
    if ("+".equals(operation)) {
        double result = firstNumber + secondNumber;
            String answer = Double.toString(result);
            txtDisplay.setText(answer);
    }
    else if ("-".equals(operation))  {
        double result = firstNumber - secondNumber;
            String answer = Double.toString(result);
            txtDisplay.setText(answer);

}
       else if ("*".equals(operation))  {
        double result = firstNumber * secondNumber;
            String answer = Double.toString(result);
            txtDisplay.setText(answer);

}
       else  {
        double result = firstNumber / secondNumber;
            String answer = Double.toString(result);
            txtDisplay.setText(answer);

}
}

private void btnSignActionPerformed(java.awt.event.ActionEvent evt) {
    String number = txtDisplay.getText();
    double number1 = Double.parseDouble(number);
    number1 = number1 * (-1);
    txtDisplay.setText(String.valueOf(number1));
}

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        /* Create and display the form */
          "Look and feel spoiler thingy"
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new GUI().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify
    private javax.swing.JButton btn0;
    private javax.swing.JButton btn1;
    private javax.swing.JButton btn2;
    private javax.swing.JButton btn3;
    private javax.swing.JButton btn4;
    private javax.swing.JButton btn5;
    private javax.swing.JButton btn6;
    private javax.swing.JButton btn7;
    private javax.swing.JButton btn8;
    private javax.swing.JButton btn9;
    private javax.swing.JButton btnClr;
    private javax.swing.JButton btnDiv;
    private javax.swing.JButton btnEq;
    private javax.swing.JButton btnMns;
    private javax.swing.JButton btnMulti;
    private javax.swing.JButton btnPlus;
    private javax.swing.JButton btnPt;
    private javax.swing.JButton btnSign;
    private javax.swing.JTextField txtDisplay;
    // End of variables declaration
}