A simple JavaFX calculator

Calc.java

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.property.*;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.input.KeyEvent;
import javafx.scene.layout.*;
import javafx.stage.*;

import java.util.*;

// a simple JavaFX calculator.
public class Calc extends Application {
    private static final String[][] template = {
            {"7", "8", "9", "/"},
            {"4", "5", "6", "*"},
            {"1", "2", "3", "-"},
            {"0", "c", "=", "+"}
    };

    private final Map<String, Button> accelerators = new HashMap<>();

    private final DoubleProperty stackValue = new SimpleDoubleProperty();
    private final DoubleProperty value = new SimpleDoubleProperty();

    private enum Op {NOOP, ADD, SUBTRACT, MULTIPLY, DIVIDE}

    private Op curOp = Op.NOOP;
    private Op stackOp = Op.NOOP;

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

    @Override
    public void start(Stage stage) {
        final TextField screen = createScreen();
        final TilePane buttons = createButtons();

        stage.setTitle("Calc");
        stage.initStyle(StageStyle.UTILITY);
        stage.setResizable(false);
        stage.setScene(new Scene(createLayout(screen, buttons)));
        stage.show();
    }

    private VBox createLayout(TextField screen, TilePane buttons) {
        final VBox layout = new VBox(20);
        layout.setAlignment(Pos.CENTER);
        layout.setStyle("-fx-background-color: chocolate; -fx-padding: 20; -fx-font-size: 20;");
        layout.getChildren().setAll(screen, buttons);
        handleAccelerators(layout);
        screen.prefWidthProperty().bind(buttons.widthProperty());
        return layout;
    }

    private void handleAccelerators(VBox layout) {
        layout.addEventFilter(KeyEvent.KEY_PRESSED, keyEvent -> {
            Button activated = accelerators.get(keyEvent.getText());
            if (activated != null) {
                activated.fire();
            }
        });
    }

    private TextField createScreen() {
        final TextField screen = new TextField();
        screen.setStyle("-fx-background-color: aquamarine;");
        screen.setAlignment(Pos.CENTER_RIGHT);
        screen.setEditable(false);
        screen.textProperty().bind(Bindings.format("%.0f", value));
        return screen;
    }

    private TilePane createButtons() {
        TilePane buttons = new TilePane();
        buttons.setVgap(7);
        buttons.setHgap(7);
        buttons.setPrefColumns(template[0].length);
        for (String[] r : template) {
            for (String s : r) {
                buttons.getChildren().add(createButton(s));
            }
        }
        return buttons;
    }

    private Button createButton(final String s) {
        Button button = makeStandardButton(s);

        if (s.matches("[0-9]")) {
            makeNumericButton(s, button);
        } else {
            final ObjectProperty<Op> triggerOp = determineOperand(s);
            if (triggerOp.get() != Op.NOOP) {
                makeOperandButton(button, triggerOp);
            } else if ("c".equals(s)) {
                makeClearButton(button);
            } else if ("=".equals(s)) {
                makeEqualsButton(button);
            }
        }

        return button;
    }

    private ObjectProperty<Op> determineOperand(String s) {
        final ObjectProperty<Op> triggerOp = new SimpleObjectProperty<>(Op.NOOP);
        switch (s) {
            case "+" -> triggerOp.set(Op.ADD);
            case "-" -> triggerOp.set(Op.SUBTRACT);
            case "*" -> triggerOp.set(Op.MULTIPLY);
            case "/" -> triggerOp.set(Op.DIVIDE);
        }
        return triggerOp;
    }

    private void makeOperandButton(Button button, final ObjectProperty<Op> triggerOp) {
        button.setStyle("-fx-base: lightgray;");
        button.setOnAction(actionEvent -> curOp = triggerOp.get());
    }

    private Button makeStandardButton(String s) {
        Button button = new Button(s);
        button.setStyle("-fx-base: beige;");
        accelerators.put(s, button);
        button.setMaxSize(Double.MAX_VALUE, Double.MAX_VALUE);
        return button;
    }

    private void makeNumericButton(final String s, Button button) {
        button.setOnAction(actionEvent -> {
            if (curOp == Op.NOOP) {
                value.set(value.get() * 10 + Integer.parseInt(s));
            } else {
                stackValue.set(value.get());
                value.set(Integer.parseInt(s));
                stackOp = curOp;
                curOp = Op.NOOP;
            }
        });
    }

    private void makeClearButton(Button button) {
        button.setStyle("-fx-base: mistyrose;");
        button.setOnAction(actionEvent -> value.set(0));
    }

    private void makeEqualsButton(Button button) {
        button.setStyle("-fx-base: ghostwhite;");
        button.setOnAction(actionEvent -> {
            switch (stackOp) {
                case ADD -> value.set(stackValue.get() + value.get());
                case SUBTRACT -> value.set(stackValue.get() - value.get());
                case MULTIPLY -> value.set(stackValue.get() * value.get());
                case DIVIDE -> value.set(stackValue.get() / value.get());
            }
        });
    }
}

Can anybody tell us how can we make the sum of more than two numbers in above mentioned code?

Can anybody tell us how can we make the sum of more than two numbers in above mentioned code?

@Kapil-Joban did you read @jewelsea's comment dated Mar 9, 2018? The shunting-yard algorithm is proposed in that comment.

Can anybody tell us how can we make the sum of more than two numbers in above mentioned code?

@Kapil-Joban , You can also have a look at javax ScriptEngineManager. I guess it still works. I am not sure. https://github.com/sedj601/CalculatorFX2/blob/master/CalculatorController.java