Calculadora En Java Fx

/*
* Calculadora simple en JavaFX
*
*
* Autora Damaris
*/

import javafx.ext.swing.*;
import javafx.stage.Stage;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.input.*;import javafx.scene.layout.*;
import javafx.scene.paint.*;
import javafx.scene.shape.*;
import javafx.scene.text.*;
import javafx.scene.transform.*;

var str : String = "";
var tmp : String = "";
var left : Number = 0.0;
var right :Number = 0.0;
var operator : String = "";
var flush : Boolean = false;

// button gradient
def buttonGradient = LinearGradient {
startX: 0.0,
startY: 0.0,
endX: 0.0,
endY: 1.0
stops: [Stop {
offset: 0.0
color: Color.rgb(166, 166, 168)
},
Stop {
offset: 1.0
color: Color.rgb(122, 122, 122)
}
]
};

// background gradientdef backgroundGradient = LinearGradient {
startX: 0.0,
startY: 0.0,
endX: 0.5,
endY: 1.0
stops: [
Stop {
offset: 0.0
color: Color.rgb(128, 128, 64)
},Stop {
offset: 1.0
color: Color.rgb(128, 128, 0)
}
]
};

def keyLabels = [
"7", "8", "9", "/", "sqrt",
"4", "5", "6", "x", "%",
"1", "2", "3", "-","1/x",
"0", "+/-", ".", "+", "="
];

Stage {

title: "Calculator"
resizable : false

scene: Scene {
content: [
// background
Rectangle {width: 240
height: 260
arcWidth: 10
arcHeight: 10
fill: backgroundGradient
},

// panels, built on top of the background
VBox {transforms: bind Translate.translate(20, 20)
spacing: 10
content: [
// display panel
buildDisplayPanel(),

// Backspace, CE and C buttons panelHBox {
spacing: 5
content: [
// Backspace button
buildBackspaceButton(),

// CE button
buildCEButton(),...