A brief description of a program I am building. The program has 3 classes, a user class, a port class, and a vehicle class.
The port class contains an Id property of String type and Arraylist property that contains all onsite vehicles. The Vehicle class contains an Id property and another property of Port class called current_port. The Vehicle class is a superclass to the ship class and the truck class, which in turns is a superclass for the basic truck class and the tanker class. Using ObjectInputStream and ObjectOutputStream, both classes have method that allows for the entry of their objects into their respective files.
For the Port class, I have no issue with writing, appending, reading, and updating its object in its file. However, the problem surfaces when I try to create an object of basic truck and tanker type. Specifically, when a new vehicle is created, the file of the port class is updated to reflect the inclusion of another vehicle.The problem surfaces when I create an object of basic truck class and tanker class. While I am able to write them into the vehicle file and update the port file, when I try to read all retrieve all vehicles from the vehicle file, I got the following exception. This exception only appears when I create vehicles of basic truck and tanker type:
Exception in thread "main" java.lang.ClassCastException: class java.lang.String cannot be cast to class java.io.ObjectStreamClass (java.lang.String and java.io.ObjectStreamClass are in module java.base of loader 'bootstrap')
at java.base/java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1924)
at java.base/java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:2075)
at java.base/java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1922)
at java.base/java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2248)
at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1757)
at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:538)
at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:496)
at java.base/java.util.ArrayList.readObject(ArrayList.java:899)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:577)
at java.base/java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:1100)
at java.base/java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:2447)
at java.base/java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2281)
at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1757)
at java.base/java.io.ObjectInputStream$FieldValues.<init>(ObjectInputStream.java:2630)
at java.base/java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:2481)
at java.base/java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2281)
at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1757)
at java.base/java.io.ObjectInputStream$FieldValues.<init>(ObjectInputStream.java:2630)
at java.base/java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:2481)
at java.base/java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2281)
at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1757)
at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:538)
at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:496)
at Vehicle.getVehicles(Vehicle.java:20)
at Main.main(Main.java:8)
The following is my code:
AppendObjectOutputStream
public class AppendObjectOutputStream extends ObjectOutputStream {
AppendObjectOutputStream() throws IOException
{
// Super keyword refers to parent class instance
super();
}
// Constructor of this class
// 1. Parameterized constructor
AppendObjectOutputStream(OutputStream o) throws IOException
{
super(o);
}
// Method of this class
public void writeStreamHeader() throws IOException
{
return;
}
}
Port Class:
import java.io.*;
import java.util.ArrayList;
import java.util.Random;
import java.util.Scanner;
public class Port implements Serializable {
public String Pid;
public ArrayList<Vehicle>vehicles = new ArrayList<Vehicle>();
public Port(String Pid){
this.Pid = Pid;}
public boolean equals(Port port) {
if (port == this) {
System.out.println("true");
return true;
}
return this.Pid.equals(port.Pid);
}
public static ArrayList<Port> getPorts(){
ArrayList<Port> port_list = new ArrayList<Port>();
try {
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("port.txt"));
while (true){
try{
Port port = (Port) ois.readObject();
port_list.add(port);
} catch (EOFException e){
break;
}
catch (ClassNotFoundException e){
e.printStackTrace();
}
}
} catch (FileNotFoundException e){
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}
return port_list;
}
public static void inputPortIntoFile(File file, Port port){
if (file.length() == 0){
try{
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("port.txt"));
oos.writeObject(port);
oos.close();
} catch (FileNotFoundException e){
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}
}
else {
try{
AppendObjectOutputStream oos = new AppendObjectOutputStream(new FileOutputStream("port.txt", true));
oos.writeObject(port);
oos.close();
} catch (FileNotFoundException e){
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}
}
}
public static void updatePort(Port port){
System.out.println(port.vehicles);
ArrayList<Port> port_list = Port.getPorts();
File file = new File("port.txt");
for (int i =0; i<port_list.size(); i++){
if (port_list.get(i).equals(port)){
port_list.set(i, port);
}
}
file.delete();
try{
file.createNewFile();
for (Port p: port_list){
Port.inputPortIntoFile(file, p);
}
} catch (IOException e){
e.printStackTrace();
}
}
public static Port queryPortbyID(String Pid){
for (Port port: getPorts()){
if (port.Pid.equals(Pid)){
return port;
}
}
System.out.println("This port does not exist");
return null;
}
public static void createNewPort(){
String Pid = "";
Random random = new Random();
for (int i = 1; i<=10; i++){
Pid = Pid + random.nextInt(10);
}
File file = new File("port.txt");
Port new_port = new Port(Pid);
inputPortIntoFile(file, new_port);
}
public void accept_vehicles(Vehicle vehicle){
this.vehicles.add(vehicle);
Port.updatePort(this);
}
}
Vehicle Class:
import java.io.*;
import java.util.ArrayList;
import java.util.Random;
import java.util.Scanner;
public class Vehicle implements Serializable {
public String Vid;
public Port current_port;
public Vehicle(String Vid, Port port){
this.Vid = Vid;
this.current_port = port;
}
public static ArrayList<Vehicle> getVehicles(){
ArrayList<Vehicle> vehicle_list = new ArrayList<Vehicle>();
try {
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("vehicle.txt"));
while (true){
try {
Vehicle vehicle = (Vehicle) ois.readObject();
System.out.println(vehicle);
vehicle_list.add(vehicle);
} catch (EOFException e){
break;
} catch (ClassNotFoundException e){
e.printStackTrace();
}
}
} catch (FileNotFoundException e){
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}
return vehicle_list;
}
public static void inputVehicleIntoFile(File file, Vehicle vehicle){
if (file.length() == 0 ){
try{
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("vehicle.txt"));
oos.writeObject(vehicle);
oos.close();
} catch (FileNotFoundException e){
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}
}
else {
try{
AppendObjectOutputStream oos = new AppendObjectOutputStream(new FileOutputStream("vehicle.txt", true));
oos.writeObject(vehicle);
oos.close();
} catch (FileNotFoundException e){
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}
}
}
public static Vehicle queryVehiclebyID(String Vid){
for (Vehicle vehicle: Vehicle.getVehicles()){
if (vehicle.Vid.equals(Vid)){
return vehicle;
}
}
System.out.println("Vehicle not found");
return null;
}
public static Vehicle createNewVehicle(){
Scanner scanner = new Scanner(System.in);
String Vid = "";
Random random = new Random();
File file = new File("vehicle.txt");
for (int i = 1; i<=10; i++){
Vid = Vid + random.nextInt(10);
}
System.out.println("Please ionput the id of the port you would like to assign this vehicle to");
String Pid = scanner.nextLine();
Port port = Port.queryPortbyID(Pid);
System.out.println("Please input the type of vehicle (ship/basic/tanker)");
String type = scanner.nextLine();
if (type.equals("ship")){
Vehicle vehicle = new ship("SH"+Vid, port);
inputVehicleIntoFile(file, vehicle);
return vehicle;
}
else if (type.equals("basic")){
Vehicle vehicle = new basic("BT"+Vid, port);
inputVehicleIntoFile(file, vehicle);
return vehicle;
}
else {
Vehicle vehicle = new tanker("TT"+Vid, port);
inputVehicleIntoFile(file, vehicle);
return vehicle;
}
}
}
class ship extends Vehicle{
public ship(String Vid, Port port){
super(Vid, port);
}
}
class truck extends Vehicle{
public truck(String Vid, Port port){
super(Vid, port);
}
}
class tanker extends truck{
public tanker(String Vid, Port port){
super(Vid, port);
}
}
class basic extends truck{
public basic(String Vid, Port port){
super(Vid, port);
}
}
User Class
public class User {
public static void addPort(){
Port.createNewPort();
}
public static void addVehicle(){
Vehicle new_vehicle = Vehicle.createNewVehicle();
new_vehicle.current_port.accept_vehicles(new_vehicle);
}
}
Main Class
public class Main {
public static void main(String[] args) {
User.addPort();
User.addVehicle();
User.addVehicle();
User.addVehicle();
Vehicle.getVehicles();
}
}
Do you know what could have caused this issue and how can I fix it? Thank you very much
