Calculator/CalculatorControl.java

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.TextArea;

public class CalculatorControl {

    @FXML
    private TextArea display;

    private double firstNumber;
    private double secondNumber;
    private String operation;
    private boolean awaitingSecondNumber;

    @FXML
    void onClearButtonClicked(ActionEvent event) {
        display.clear();
        firstNumber = 0;
        secondNumber = 0;
        operation = null;
        awaitingSecondNumber = false;
    }

    @FXML
    void onClearEntryButtonClicked(ActionEvent event) {
        display.clear();
    }

    @FXML
    void onDeleteButtonClicked(ActionEvent event) {
        String currentText = display.getText();
        if (currentText != null && !currentText.isEmpty()) {
            display.setText(currentText.substring(0, currentText.length() - 1));
        }
    }

    @FXML
    void onEqualsButtonClicked(ActionEvent event) {
        if (awaitingSecondNumber) {
            String displayText = display.getText();
            String[] parts = displayText.split(" ");
            try {
                secondNumber = Double.parseDouble(parts[parts.length - 1]);
                switch (operation) {
                    case "+":
                        display.setText(firstNumber + " + " + secondNumber + " = " + (firstNumber + secondNumber));
                        break;
                    case "-":
                        display.setText(firstNumber + " - " + secondNumber + " = " + (firstNumber - secondNumber));
                        break;
                    case "*":
                        display.setText(firstNumber + " * " + secondNumber + " = " + (firstNumber * secondNumber));
                        break;
                    case "/":
                        if (secondNumber == 0) {
                            display.setText("Error");
                        } else {
                            display.setText(firstNumber + " / " + secondNumber + " = " + (firstNumber / secondNumber));
                        }
                        break;
                    case "%":
                        display.setText(firstNumber + " % " + secondNumber + " = " + (firstNumber % secondNumber));
                        break;
                }
                awaitingSecondNumber = false;
            } catch (NumberFormatException e) {
                display.setText("Error");
            }
        }
    }

    @FXML
    void onNumberButtonClicked(ActionEvent event) {
        Button button = (Button) event.getSource();
        String buttonText = button.getText();
        display.appendText(buttonText);
    }

    @FXML
    void onOperationButtonClicked(ActionEvent event) {
        Button button = (Button) event.getSource();
        String buttonText = button.getText();
        if (!awaitingSecondNumber) {
            String displayText = display.getText();
            String[] parts = displayText.split(" ");
            try {
                firstNumber = Double.parseDouble(parts[parts.length - 1]);
                operation = buttonText;
                awaitingSecondNumber = true;
                display.appendText(" " + buttonText + " ");
            } catch (NumberFormatException e) {
                display.setText("Error");
            }
        }
    }
}