JavaFx program to convert decimal to binary,decimal to hex, hex to decimal, binary to decimal.Recursive methods. Have written the program but keep getting Exceptions. Can anyone help me with this code, as my brainpower is dropping by the second :) Code is rovided below:

public class Converter extends Application{

private double paneWidth=500;

private double paneHeight=100;

@Override // Override startmethod

public void start(Stage primaryStage) {

TextField tfInput = new TextField(); // Inputfield

tfInput.setPromptText("Number to be converted..."); // Prompttext background tf

tfInput.getText();

TextField tfOutput = new TextField(); // Outputfield

Button btdecBin = new Button("Decimal to Binary");

Button btdecHex = new Button("Decimal to Hex");

Button btbinDec = new Button("Binary to Decimal");

Button bthexDec = new Button("Hex to Decimal");

HBox buttonBox = new HBox();

buttonBox.getChildren().addAll(btdecBin, btdecHex,bthexDec,btbinDec);

buttonBox.setAlignment(Pos.CENTER);

BorderPane buttons = new BorderPane();

buttons.setTop(buttonBox);

// New pane, add textfield,textarea and button

GridPane pane = new GridPane();

pane.setAlignment(Pos.CENTER);

pane.add(tfInput, 0, 3);

pane.add(tfOutput, 0, 4);

pane.add(buttons, 0, 0);

// Create a scene and place it in the stage

Scene scene = new Scene(pane, paneWidth, paneHeight);

primaryStage.setTitle("Converter"); // Set the stage title

primaryStage.setResizable(false);// No resizable

primaryStage.setScene(scene); // Place the scene in the stage

primaryStage.show(); // Display the stage

int value = Integer.parseInt(tfInput.getText());

String hexString = tfInput.getText();

String binary = tfInput.getText();

// Eventhandler for button DECIMAL TO BINARY

btdecBin.setOnAction(new EventHandler() {

public void handle(ActionEvent event) {

tfOutput.appendText("The Binary equivalent of "+value+" is "+ dec2Bin(value));

}});

// Eventhandler for button DECIMAL TO HEX

btdecHex.setOnAction(new EventHandler() {

public void handle(ActionEvent event) {

tfOutput.appendText("The HEX equivalent of "+value+" is "+ dec2Hex(value));

}});

// Eventhandler for button BINARY TO DECIMAL

btbinDec.setOnAction(new EventHandler() {

public void handle(ActionEvent event) {

tfOutput.appendText("The equivalent of "+binary+" is "+ bin2Dec(binary));

}});

//Eventhandler for button HEX TO DECIMAL

bthexDec.setOnAction(new EventHandler() {

public void handle(ActionEvent event) {

tfOutput.appendText("The Decimal equivalent of "+hexString+" is "+ hex2Dec(hexString));

}});}

//method for converting decimal to binary

private String dec2Bin(int value) {

String result= "";

return dec2Bin(value,result);

}

//Helpermethod

private String dec2Bin(int value,String result){

if (value/2 == 0){ // Basecase

return (value%2)+result;

}

else

return dec2Bin(value/2,(value%2)+result);

}

// Method converting decimal to hex

private String dec2Hex(int value) {

String result = "";

return dec2Hex(value, result);

}

/** Recursive helper method */

private String dec2Hex(int value, String result) {

int r = value % 16; // Remainder

String remainder = r >= 10 ?

String.valueOf((char)('A' + r % 10)) : String.valueOf(r);

if (value / 16 == 0) // Base case

return remainder + result;

else

return dec2Hex(value / 16, remainder + result); // Recursive call

}

/** Method parses a hex number as

* string into a decimal integer */

private int hex2Dec(String hexString) {

int result = 0;

int index = 0;

int n = hexString.length() - 1;

return hex2Dec(hexString, index, n, result);

}

/** Recursive helper method */

private int hex2Dec(String hexString, int index, int n, int result) {

int dec = 0; // Decimal conversion

if (hexString.charAt(index) >= 'A' &&

hexString.charAt(index)

dec = (hexString.charAt(index) - 'A') + 10;

}

else {

dec = Integer.parseInt(String.valueOf(hexString.charAt(index)));

}

dec *= (int)Math.pow(16, n);

if (n == 0) // Base Case

return result + dec;

else // Recursive call

return hex2Dec(hexString, index + 1, n - 1, dec + result);

}

private int bin2Dec(String s) {

int i = (s.charAt(0) == '1') ? 1 : 0;

if (s.length() == 1)

return i;

return (int)Math.pow(2, s.length() - 1) * i + bin2Dec(s.substring(1));

}

public static void main(String[] args) { // Main method

System.out.println("");

launch(args);

}}

Converter Decimal to Binary Decimal to Hex Hex to Decimal Binary to Decimal Number to be converted