Den stora tråden för snabba nybörjarfrågor[Java]

package sample;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;

import javafx.scene.control.TextField;

import javafx.stage.Stage;


import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.URL;
import java.util.*;

public class Controller implements Initializable {

@FXML
private TextField messageField_ID;
@FXML
private TextField messageField_TIME;

@FXML
private Button nextButton;
@FXML
private Button continueButton;

private static Formatter output;


@Override
public void initialize(URL location, ResourceBundle resources) {
nextButton.setStyle("--fx-background.color: BLACK");


}

@FXML

private void handleButton(ActionEvent ae) {
Node node = (Node) ae.getSource();
Stage stage = (Stage) node.getScene().getWindow();
FXMLLoader loader = new FXMLLoader(getClass().getResource("sampleAgain.fxm l"));
Parent root = null;
try {
root = loader.load();
} catch (IOException e) {
e.printStackTrace();
}
Scene scene = new Scene(root);

stage.setScene(scene);

}

public static void newFile() {

try {
output = new Formatter("laptimes.txt");
} catch (SecurityException securityException) {
System.err.println("Denied: " + securityException);
System.exit(1);

} catch (FileNotFoundException fileNotFoundException) {
System.err.println("Could not open file: " + fileNotFoundException);
System.exit(1);

}
}

@FXML
private void addInformation(ActionEvent ae) {

try {
output.format("%d %s", messageField_ID, messageField_TIME);
} catch (FormatterClosedException formatterClosedException) {
System.err.println("Error writing to file" + formatterClosedException);

} catch (NoSuchElementException noSuchElementException) {
System.err.println("Not a valid input:" + noSuchElementException);

}
}

package sample;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

import java.io.IOException;
import java.net.URL;
import java.util.ResourceBundle;


public class Controller2 implements Initializable {


@Override
public void initialize(URL location, ResourceBundle resources) {

}
@FXML
private void handleButton2(ActionEvent ae) {
Node node = (Node)ae.getSource();
Stage stage = (Stage)node.getScene().getWindow();
FXMLLoader loader = new FXMLLoader(getClass().getResource("sample.fxml"));
Parent root = null;
try {
root = loader.load();
} catch (IOException e) {
e.printStackTrace();
}
Scene scene = new Scene(root);

stage.setScene(scene);




}
}

package sample;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class Main extends Application {

@Override
public void start(Stage primaryStage) throws Exception{
Parent root = FXMLLoader.load(getClass().getResource("sample.fxm l"));
primaryStage.setTitle("CarApp");
primaryStage.setScene(new Scene(root));
primaryStage.show();
root.setStyle("--fx-background.color: BLACK");
}


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

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.111" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
<children>
<Button fx:id="nextButton" layoutX="442.0" layoutY="308.0" mnemonicParsing="false" onAction="#handleButton" text="Next" />
<TextField fx:id="messageField_ID" layoutX="133.0" layoutY="83.0" promptText="Enter car ID" />
<TextField fx:id="messageField_Time" layoutX="133.0" layoutY="141.0" promptText="Enter laptime" />
<Button fx:id="continueButton" layoutX="353.0" layoutY="114.0" mnemonicParsing="false" onAction="#addInformation" text="Continue" />
</children>
</AnchorPane>

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.TextArea?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.111" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller2">
<children>
<Button fx:id="back" layoutX="31.0" layoutY="338.0" mnemonicParsing="false" onAction="#handleButton2" text="Back" />
<TextArea fx:id="textarea" layoutX="106.0" layoutY="16.0" prefHeight="348.0" prefWidth="426.0" />
</children>
</AnchorPane>

@FXML
private void createAccount() {
try {
output = new ObjectOutputStream(Files.newOutputStream(Paths.get ("bankaccount.ser")));
}
catch (IOException e) {
System.exit(1);
}
try {
System.out.println(Integer.parseInt(msgAccountNr.g etText()));
Account account = new Account(Integer.parseInt(msgAccountNr.getText()),m sgAccountName.getText(),
Double.parseDouble(amount.getText()));




output.writeObject(account);


}
catch (IOException e) {
e.printStackTrace();
}
catch (NoSuchElementException elementException) {

} catch(NumberFormatException eNum){
Alert alert = new Alert(AlertType.ERROR, "Invalid input. ");
alert.show();
}




//Öppna fil nedan

try {
input = new ObjectInputStream(Files.newInputStream(Paths.get(" bankaccount.ser")));
}
catch (IOException e){
}
try{
Account account = (Account) input.readObject();

msgAccountName.setText(account.getName());
msgAccountNr.setText(String.valueOf(account.getAcc ountNumber()));
balance.setText(String.valueOf(account.getBalance( )));



}
catch (IOException e1){
System.out.println("Error reading file:");
}
catch (ClassNotFoundException classNotFoundException){
System.err.println("Invalid object type:");
}catch (NumberFormatException numE){
throw numE;

}

}