is this code working

import javafx.application.Application;

import javafx.event.ActionEvent;

import javafx.event.EventHandler;

import javafx.scene.Scene;

import javafx.scene.control.Button;

import javafx.scene.control.TextField;

import javafx.scene.layout.BorderPane;

import javafx.scene.layout.ColumnConstraints;

import javafx.scene.layout.GridPane;

import javafx.scene.layout.Priority;

import javafx.stage.Stage;

import javafx.geometry.Insets;

import javafx.geometry.Pos;

public class JavaFXCalculator extends Application $\{$

private TextField tfDisplay;

private Button$[]$ btns;

private Button btnDot;

private Button btnPercent;

private Button btnSqrt;

private Button btnBackspace;

private String$[]$ btnLabels $=\{$

$"7","8","9","+",$

$"4","5","6","-",$

$"1","2","3","$x$",$

$"$C$","0","=","/"$

$\}$;

private int result $=0$;

private String inStr $="0"$;

private char lastOperator $=\text{'}\text{'}$;

EventHandler handler $=$ evt $->\{$

String currentBtnLabel $=(($Button$)$ evt.getSource$()).$getText$()$;

switch $($currentBtnLabel$)\{$

case $"0"$:

case $"1"$:

case $"2"$:

case $"3"$:

case $"4"$:

case $"5"$:

case $"6"$:

case $"7"$:

case $"8"$:

case $"9"$:

if $($inStr$.$equals$("0"))\{$

inStr $=$ currentBtnLabel;

$\}$ else $\{$

inStr $+=$ currentBtnLabel;

$\}$

tfDisplay.setText$($inStr$)$;

if $($lastOperator $==\text{'}=\text{'})\{$

result $=0$;

lastOperator $=\text{'}\text{'}$;

$\}$

break;

case $"+"$:

compute$()$;

lastOperator $=\text{'}+\text{'}$;

break;

case $"-"$:

compute$()$;

lastOperator $=\text{'}-\text{'}$;

break;

case $"$x$"$:

compute$()$;

lastOperator $=\text{'}*\text{'}$;

break;

case $"/"$:

compute$()$;

lastOperator $=\text{'}/\text{'}$;

break;

case $"="$:

compute$()$;

lastOperator $=\text{'}=\text{'}$;

break;

case $"$C$"$:

result $=0$;

inStr $="0"$;

lastOperator $=\text{'}\text{'}$;

tfDisplay.setText$("0")$;

break;

case $"."$:

if $(!$inStr.contains$("."))\{$

inStr $+=$ currentBtnLabel;

tfDisplay.setText$($inStr$)$;

$\}$

break;

case $"\%"$:

double percentage $=$ Double.parseDouble$($inStr$)/100\mathrm{.}0$;

inStr $=$ Double.toString$($percentage$)$;

tfDisplay.setText$($inStr$)$;

break;

case $""$:

double sqrtResult $=$ Math.sqrt$($Double$.$parseDouble$($inStr$))$;

inStr $=$ Double.toString$($sqrtResult$)$;

tfDisplay.setText$($inStr$)$;

break;

case $""$:

if $($inStr$.$length$()>1)\{$

inStr $=$ inStr.substring$(0,$ inStr.length$()-1)$;

$\}$ else $\{$

inStr $="0"$;

$\}$

tfDisplay.setText$($inStr$)$;

break;

$\}$

$\}$;

private void compute$()\{$

int inNum $=$ Integer.parseInt$($inStr$)$;

inStr $="0"$;

if $($lastOperator $==\text{'}\text{'})\{$

result $=$ inNum;

$\}$ else if $($lastOperator $==\text{'}+\text{'})\{$

result $+=$ inNum;

$\}$ else if $($lastOperator $==\text{'}-\text{'})\{$

result $-=$ inNum;

$\}$ else if $($lastOperator $==\text{'}*\text{'})\{$

result $*=$ inNum;

$\}$ else if $($lastOperator $==\text{'}/\text{'})\{$

result $/=$ inNum;

$\}$ else if $($lastOperator $==\text{'}=\text{'})\{$

$//$ Keep the result for the next operation

$\}$

tfDisplay.setText$($result $+"")$;

$\}$

@Override

public void start$($Stage primaryStage$)\{$

tfDisplay $=$ new TextField$("0")$;

tfDisplay.setEditable$($false$)$;

tfDisplay.setAlignment$($Pos$.$CENTER$\_$RIGHT$)$;

int numCols $=4$;

int numRows $=5$;

GridPane paneButton $=$ new GridPane$()$;

paneButton.setPadding$($new Insets$(15,0,15,0))$;

paneButton.setVgap$(5)$;

paneButton.setHgap$(5)$;

ColumnConstraints$[]$ columns $=$ new ColumnConstraints$[$numCols$]$;

for $($int i $=0$; i $<$ numCols; $++$i$)\{$

columns$[$i$]=$ new ColumnConstraints$()$;

columns$[$i$].$setHgrow$($Priority$.$ALWAYS$)$;

columns$[$i$].$setFillWidth$($true$)$;

paneButton.getColumnConstraints$().$add$($columns$[$i$])$;

$\}$

btns $=$ new Button$[16]$;

for $($int i $=0$; i $<$ btns$.$length; $++$i$)\{$

btns$[$i$]=$ new Button$($btnLabels$[$i$])$;

btns$[$i$].$setOnAction$($handler$)$;

b