baler calculator

package sample;

import java.util.Scanner;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Cursor;
import javafx.scene.control.Hyperlink;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import  javafx.scene.layout.*;
import javafx.scene.layout.StackPane;
//import javafx.scene.control.TextField;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.control.Label;
//import javafx.scene.layout.VBox;
import javafx.stage.Stage;

import java.io.FileInputStream;

public class calculator extends Application {

    int firstnumber ;
    int secondnumber;
    int solution=0;

    String display,operator,solution2;

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

    @Override
    public void start(Stage primaryStage) {

        firstnumber = 0;

        operator = "a";

        display = "0";

        //textfield creat
        TextField ansfield = new TextField();
        ansfield.setText(display);

        //button ceeat
        Button button1 = new Button("1");
        Button button2 = new Button("2");
        Button button3 = new Button("3");
        Button button4 = new Button("4");
        Button button5 = new Button("5");
        Button button6 = new Button("6");
        Button button7 = new Button("7");
        Button button8 = new Button("8");
        Button button9 = new Button("9");
        Button button0 = new Button("0");
        Button add = new Button("+");
        Button subtract = new Button("-");
        Button multiply = new Button("*");
        Button divide = new Button("/");
        Button equal = new Button("=");

        //setting up button action
        button1.setOnAction(e->{

            if(operator=="a"){
                firstnumber =firstnumber*10+1;

                System.out.println(firstnumber);

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }
            else{
                secondnumber = secondnumber*10+1;

                System.out.println(secondnumber);

                display = Integer.toString(secondnumber);

                ansfield.setText(display);
            }

        });

        button2.setOnAction(e->{

            if(operator=="a"){
                firstnumber =firstnumber*10+2;

                System.out.println(firstnumber);

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }
            else{
                secondnumber = secondnumber*10+2;

                System.out.println(secondnumber);

                display = Integer.toString(secondnumber);

                ansfield.setText(display);
            }

        });

        button3.setOnAction(e->{

            if(operator=="a"){
                firstnumber =firstnumber*10+3;

                System.out.println(firstnumber);

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }
            else{
                secondnumber = secondnumber*10+3;

                System.out.println(secondnumber);

                display = Integer.toString(secondnumber);

                ansfield.setText(display);
            }

        });

        button4.setOnAction(e->{

            if(operator=="a"){
                firstnumber =firstnumber*10+4;

                System.out.println(firstnumber);

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }
            else{
                secondnumber = secondnumber*10+4;

                System.out.println(secondnumber);

                display = Integer.toString(secondnumber);

                ansfield.setText(display);
            }

        });

        button5.setOnAction(e->{

            if(operator=="a"){
                firstnumber =firstnumber*10+5;

                System.out.println(firstnumber);

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }
            else{
                secondnumber = secondnumber*10+5;

                System.out.println(secondnumber);

                display = Integer.toString(secondnumber);

                ansfield.setText(display);
            }

        });

        button6.setOnAction(e->{

            if(operator=="a"){
                firstnumber =firstnumber*10+6;

                System.out.println(firstnumber);

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }
            else{
                secondnumber = secondnumber*10+6;

                System.out.println(secondnumber);

                display = Integer.toString(secondnumber);

                ansfield.setText(display);
            }

        });

        button7.setOnAction(e->{

            if(operator=="a"){
                firstnumber =firstnumber*10+7;

                System.out.println(firstnumber);

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }
            else{
                secondnumber = secondnumber*10+7;

                System.out.println(secondnumber);

                display = Integer.toString(secondnumber);

                ansfield.setText(display);
            }

        });

        button7.setOnAction(e->{

            if(operator=="a"){
                firstnumber =firstnumber*10+7;

                System.out.println(firstnumber);

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }
            else{
                secondnumber = secondnumber*10+7;

                System.out.println(secondnumber);

                display = Integer.toString(secondnumber);

                ansfield.setText(display);
            }

        });

        button8.setOnAction(e->{

            if(operator=="a"){
                firstnumber =firstnumber*10+8;

                System.out.println(firstnumber);

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }
            else{
                secondnumber = secondnumber*10+8;

                System.out.println(secondnumber);

                display = Integer.toString(secondnumber);

                ansfield.setText(display);
            }

        });

        button9.setOnAction(e->{

            if(operator=="a"){
                firstnumber =firstnumber*10+9;

                System.out.println(firstnumber);

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }
            else{
                secondnumber = secondnumber*10+9;

                System.out.println(secondnumber);

                display = Integer.toString(secondnumber);

                ansfield.setText(display);
            }

        });

        button0.setOnAction(e->{

            if(operator=="a"){
                firstnumber =firstnumber*10+0;

                System.out.println(firstnumber);

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }
            else{
                secondnumber = secondnumber*10+0;

                System.out.println(secondnumber);

                display = Integer.toString(secondnumber);

                ansfield.setText(display);
            }

        });

        add.setOnAction(e->{

             operator = "+";

             //firstnumber = firstnumber+secondnumber;

             display = Integer.toString(firstnumber);

            ansfield.setText(display);

             secondnumber = 0;
        });

        subtract.setOnAction(e->{

            operator = "-";

            //firstnumber = firstnumber-secondnumber;

            display = Integer.toString(firstnumber);

            ansfield.setText(display);

            secondnumber = 0;
        });

        multiply.setOnAction(e->{

            operator = "*";

            if(secondnumber!=0) {
                //firstnumber = firstnumber * secondnumber;

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }

            secondnumber = 0;
        });

        divide.setOnAction(e->{

            operator = "/";

            if(secondnumber!=0) {
                //firstnumber = firstnumber / secondnumber;

                display = Integer.toString(firstnumber);

                ansfield.setText(display);
            }

            secondnumber = 0;
        });

        equal.setOnAction(e->{

            if(operator=="+"){
                solution = firstnumber+secondnumber;

                solution2 = Integer.toString(solution);

                display = solution2;

                ansfield.setText(display);

                firstnumber = 0;
                secondnumber = 0;
            }
            if(operator=="-"){
                solution = firstnumber-secondnumber;

                solution2 = Integer.toString(solution);

                display = solution2;

                ansfield.setText(display);

                firstnumber = 0;
                secondnumber = 0;
            }
            if(operator=="*"){
                solution = firstnumber*secondnumber;

                solution2 = Integer.toString(solution);

                display = solution2;

                ansfield.setText(display);

                firstnumber = 0;
                secondnumber = 0;
            }
            if(operator=="/"){

                if(secondnumber!=0) {
                    solution = firstnumber / secondnumber;

                    solution2 = Integer.toString(solution);

                    display = solution2;

                    ansfield.setText(display);
                }
                else{
                    ansfield.setText("ERROR!");
                }

                firstnumber = 0;
                secondnumber = 0;
            }
        });

        HBox line1 = new HBox(button1 ,button2 ,button3 ,add);

        HBox line2 = new HBox(button4 ,button5 ,button6 ,subtract);

        HBox line3 = new HBox(button7 ,button8 ,button9 ,multiply);

        HBox line4 = new HBox(button0 ,equal ,divide);

        //vbox creating
        VBox container = new VBox(ansfield ,line1 ,line2 ,line3 ,line4);

        //setting scene
        Scene options = new Scene(container);

        //main window
        Stage stage = new Stage();
        stage.setTitle("calculator");
        stage.setHeight(170);
        stage.setWidth(110);

        stage.setScene(options);

        stage.show();
    }
}