[FIXED] Problem With Equations In JavaFX Calculator

Issue

I have a problem with my JavaFX/Java calculator. When I enter an equation, it(the calculator) works fine, and the answer is correct, too. But when I press/key in another operation and another number after that, the result/sum/etc. will not be correct unless the operator I pressed/keyed in is the same one as before. Here's an example:

works: 2 + 6 = 8 + 2 = 10

doesn't work: 2 + 6 = 8 - 2 = 10

works: 6 x 2 = 12 x 2 = 26

doesn't work: 6 x 2 = 12 ÷ 2 = 26

I was wondering if there was any way I could fix this.

Here's my FXML Controller class:

package calculator;

import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.input.KeyCode;
import javafx.stage.Stage;
import java.lang.Math;

public class Calculator implements Initializable {

    double data = 0d;
    int operation = -1;
    private boolean start = false;

    @FXML
    private Label display;

    @FXML
    private Button two;

    @FXML
    private Button five;

    @FXML
    private Button four;

    @FXML
    private Button three;

    @FXML
    private Button one;

    @FXML
    private Button six;

    @FXML
    private Button seven;

    @FXML
    private Button multi;

    @FXML
    private Button add;

    @FXML
    private Button divide;

    @FXML
    private Button minus;

    @FXML
    private Button equals;

    @FXML
    private Button clear;

    @FXML
    private Button zero;

    @FXML
    private Button nine;

    @FXML
    private Button eight;

    @FXML
    void handleButtonAction(ActionEvent event) {

        if(start)
        {
            display.setText("");
            start = false;
        }

        if(event.getSource() == one)
        {
            display.setText(display.getText() + "1");
        }
        else if(event.getSource() == two)
        {
            display.setText(display.getText() + "2");
        }
        else if(event.getSource() == three)
        {
            display.setText(display.getText() + "3");
        }
        else if(event.getSource() == four)
        {
            display.setText(display.getText() + "4");
        }
        else if(event.getSource() == five)
        {
            display.setText(display.getText() + "5");
        }
        else if(event.getSource() == six)
        {
            display.setText(display.getText() + "6");
        }
        else if(event.getSource() == seven)
        {
            display.setText(display.getText() + "7");
        }
        else if(event.getSource() == eight)
        {
            display.setText(display.getText() + "8");
        }
        else if(event.getSource() == nine)
        {
            display.setText(display.getText() + "9");
        }
        else if(event.getSource() == zero)
        {
            display.setText(display.getText() + "0");
        }
        else if(event.getSource() == clear)
        {
            display.setText("");
        } 
        else if(event.getSource() == add)
        {
            data = Float.parseFloat(display.getText());
            operation = 1;
            display.setText("");
        }
        else if(event.getSource() == minus)
        {
            data = Float.parseFloat(display.getText());
            operation = 2;
            display.setText("");
        }
        else if(event.getSource() == multi)
        {
            data = Float.parseFloat(display.getText());
            operation = 3;
            display.setText("");
        }
        else if(event.getSource() == divide)
        {
            data = Float.parseFloat(display.getText());
            operation = 4;
            display.setText("");
        }
        else if(event.getSource() == equals)
        {
            Float secondOperand = Float.parseFloat(display.getText());
            switch(operation)
            {
                case 1: //Addition
                    Double ans = data + secondOperand;
                    display.setText(String.valueOf(ans));
                    //data = ans;
                    break;
                case 2: //Subtraction
                    ans = data - secondOperand;
                    display.setText(String.valueOf(ans));
                    //data = ans;
                    break;
                case 3: //Multiplication
                    ans = data * secondOperand;
                    display.setText(String.valueOf(ans));
                    //data = ans;
                    break;
                case 4: //Division
                    ans = 0d;
                    try{
                    ans = data / secondOperand;
                    }catch(Exception ex){display.setText("Error");}
                    display.setText(String.valueOf(ans));
                    //data = ans;
                    break;
            }
            if(event.getSource() != divide && event.getSource() != add && event.getSource() != multi && event.getSource() != minus)
            {
                start = true;
            }
        }

    }

@FXML
    private void send2sceneconver(ActionEvent event) throws Exception{
        Parent rootBMI = FXMLLoader.load(getClass().getResource("ConversionCal.fxml"));

        Scene scene2 = new Scene(rootBMI);
        Stage calS = (Stage) ((Node) event.getSource()).getScene().getWindow();

        calS.setScene(scene2);
        calS.show();
    }

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }  

}

Any help would be appreciated.

Solution

So I'm not exactly sure why its there but the problem is with this if statment

    if(start)
    {
        display.setText("");
        start = false;
    }

I have tested it with your works vs doesn't work equations and all seems to be fine. The reason that was breaking it was it was reseting the display as it was doing the next operation so it looks fine when watching it but the data gets cleared as it trying to do the operation. so it had no last data to pull from. I commented it out and the rest seemed to work here is my class for verification

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.stage.Stage;

import java.net.URL;
import java.util.ResourceBundle;


public class Calculator implements Initializable {

    double data = 0d;
    int operation = -1;
    private boolean start = false;

    @FXML
    private Label display;

    @FXML
    private Button two;

    @FXML
    private Button five;

    @FXML
    private Button four;

    @FXML
    private Button three;

    @FXML
    private Button one;

    @FXML
    private Button six;

    @FXML
    private Button seven;

    @FXML
    private Button multi;

    @FXML
    private Button add;

    @FXML
    private Button divide;

    @FXML
    private Button minus;

    @FXML
    private Button equals;

    @FXML
    private Button clear;

    @FXML
    private Button zero;

    @FXML
    private Button nine;

    @FXML
    private Button eight;

    @FXML
    void handleButtonAction(ActionEvent event) {

//        if(start)
//        {
//            display.setText("");
//            start = false;
//        }

        if(event.getSource() == one)
        {
            display.setText(display.getText() + "1");
        }
        else if(event.getSource() == two)
        {
            display.setText(display.getText() + "2");
        }
        else if(event.getSource() == three)
        {
            display.setText(display.getText() + "3");
        }
        else if(event.getSource() == four)
        {
            display.setText(display.getText() + "4");
        }
        else if(event.getSource() == five)
        {
            display.setText(display.getText() + "5");
        }
        else if(event.getSource() == six)
        {
            display.setText(display.getText() + "6");
        }
        else if(event.getSource() == seven)
        {
            display.setText(display.getText() + "7");
        }
        else if(event.getSource() == eight)
        {
            display.setText(display.getText() + "8");
        }
        else if(event.getSource() == nine)
        {
            display.setText(display.getText() + "9");
        }
        else if(event.getSource() == zero)
        {
            display.setText(display.getText() + "0");
        }
        else if(event.getSource() == clear)
        {
            display.setText("");
        }
        else if(event.getSource() == add)
        {
            data = Float.parseFloat(display.getText());
            operation = 1;
            display.setText("");
        }
        else if(event.getSource() == minus)
        {
            data = Float.parseFloat(display.getText());
            operation = 2;
            display.setText("");
        }
        else if(event.getSource() == multi)
        {
            data = Float.parseFloat(display.getText());
            operation = 3;
            display.setText("");
        }
        else if(event.getSource() == divide)
        {
            data = Float.parseFloat(display.getText());
            operation = 4;
            display.setText("");
        }
        else if(event.getSource() == equals)
        {
            Float secondOperand = Float.parseFloat(display.getText());
            switch(operation)
            {
                case 1: //Addition
                    Double ans = data + secondOperand;
                    display.setText(String.valueOf(ans));
                    //data = ans;
                    break;
                case 2: //Subtraction
                    ans = data - secondOperand;
                    display.setText(String.valueOf(ans));
                    //data = ans;
                    break;
                case 3: //Multiplication
                    ans = data * secondOperand;
                    display.setText(String.valueOf(ans));
                    //data = ans;
                    break;
                case 4: //Division
                    ans = 0d;
                    try{
                        ans = data / secondOperand;
                    }catch(Exception ex){display.setText("Error");}
                    display.setText(String.valueOf(ans));
                    //data = ans;
                    break;
            }
//            if(event.getSource() != divide && event.getSource() != add && event.getSource() != multi && event.getSource() != minus)
//            {
//                start = true;
//            }
        }
    }

    @FXML
    private void send2sceneconver(ActionEvent event) throws Exception{
        Parent rootBMI = FXMLLoader.load(getClass().getResource("ConversionCal.fxml"));

        Scene scene2 = new Scene(rootBMI);
        Stage calS = (Stage) ((Node) event.getSource()).getScene().getWindow();

        calS.setScene(scene2);
        calS.show();
    }

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }
}

Also side note you can remove the implements Initializable if your not using it

Answered By - Matt
Answer Checked By - Clifford M. (JavaFixing Volunteer)