Please help with the connectCar, disconnectCar, and hashCode method. I need to use Doubly LinkedList for the connectCar and disconnectCar but not sure how to implement it. Thanks

import java.util.*;

class Train implements Iterable {

private String name;

private Car head = new Car(null);

public Train(String name) {

this.name = name;

}

public String getName() {

//returns the train's name

//O(1)

return name;

}

public Iterator iterator() {

//returns an iterator which traverses

//the train from the first car (the one closest

//to the front of the train) to the last car

//use an anonymous class here

//required iterator methods: next() and hasNext()

//both methods are required to work in O(1) time

return new Iterator()

{

private Car name = head;

//other private variables here, such as for helping next() and hasNext()

public Car next()

{

name = name.getNext();

return name;

}

public boolean hasNext()

{

if(name.getNext() !=null){

return true;

}

else{

return false;

}

}

};

}

public boolean equals(Object o) {

//two trains are equal if they have the same name

//O(1)

// If the object is compared with itself then return true

if (o == this) {

return true;

}

/* Check if o is an instance of Complex or not

"null instanceof [type]" also returns false */

if (!(o instanceof Train)) {

return false;

}

// typecast o to Complex so that we can compare data members

Train c = (Train) o;

// Compare the data members and return accordingly

if(name.equalsIgnoreCase(c.getName()))

return true;

else

return false;

}

public void connectCar(Car c) {

//connects the car to the end of the cars for this train

//requied Big-O: O(n) where n=the length of the linked list

//of cars starting at c, NOT n=the number of cars already

//connected to this train.

}

public Car disconnectCar(Car c) {

//returns the car disconnected from the train

//should throw the following exception if the car isn't one

//the train: RuntimeException("Can not disconnect a car that doesn't exist");

//required Big-O: O(n) where n=the number of cars on this train

return null;

}

public int hashCode() {

//returns a hashcode for a train...

//remember: if two objects are equal, they should

//have the same hashcode

//O(1)

return 0;

}

//example test code... edit this as much as you want!

public static void main(String[] args) {

Car c1 = new Car("C1");

Car c2 = new Car("C2");

c1.setNext(c2);

c2.setPrevious(c1);

Train t1 = new Train("T1");

Train t1b = new Train("T1");

if(t1.getName().equals("T1") && t1.equals(t1b) && t1.hashCode() == t1b.hashCode()) {

System.out.println("Yay 1");

}

t1.printAscii();

t1.connectCar(c1);

t1.printAscii();

Car c3 = new Car("C3");

Car c4 = new Car("C4");

c3.setNext(c4);

c4.setPrevious(c3);

t1.connectCar(c3);

t1.printAscii();

}

/*****************************************************************/

/****************** DO NOT EDIT BELOW THIS LINE ******************/

/*****************************************************************/

public String toString() {

String s = getName();

for(Car c : this) {

s += " " + c;

}

return s;

}

public void printAscii() {

/*

From: http://www.ascii-art.de/ascii/t/train.txt

o O___ _________

_][__|o| |O O O O|

<_______|-|_______|

/O-O-O o o

*/

System.out.print(String.format("%-4s",getName())+"o O___");

for(Car c : this) {

System.out.print(" _________");

}

System.out.println();

System.out.print(" _][__|o|");

for(Car c : this) {

System.out.print(" | "+String.format("%-5s",c.getName())+" |");

}

System.out.println();

System.out.print(" |_______|");

for(Car c : this) {

System.out.print("-|_______|");

}

System.out.println();

System.out.print(" /O-O-O ");

for(Car c : this) {

System.out.print(" o o ");

}

System.out.println();

}

}