Good morning everyone!!!

It was given me as a data structures project the creation of a linked list that performs basic arithmetic operations (Add, subtract, multiplication, division, and reminder) with two polynomials. Ive been having some issues to create the methods that perform the operations before mentioned. Ive been trying for almost a week and I couldnt do it. I attached my current java code; I wrote in bold the functions that I have to work on (Last class of the code) and the current output. Any advice, any guide, any help to approach this solution will be welcome.

class DNode {

private T data;

private DNode prev, next;

public DNode(T d, DNode p, DNode n) {

data = d;

next = n;

prev = p;

}

public T getData() {

return data;

}

public DNode getNext() {

return next;

}

public DNode getPrev() {

return prev;

}

public void setData(T d) {

data = d;

}

public void setNext(DNode n) {

next = n;

}

public void setPrev(DNode p) {

prev = p;

}

}

class DList {

private DNode header, trailer;

private int size;

public DList() {

size = 0;

header = new DNode(null, null, null);

trailer = new DNode(null, header, null);

header.setNext(trailer);

}

// utility methods

public int size() {

return size;

}

public boolean isEmpty() {

return size == 0;

}

// give clients access to nodes, but not to the header or trailer

public DNode getFirst() throws Exception {

if (isEmpty())

throw new Exception("Empty");

return header.getNext();

}

public DNode getLast() throws Exception {

if (isEmpty())

throw new Exception("Empty");

return trailer.getPrev();

}

public DNode getNext(DNode v) throws Exception {

DNode ans = v.getNext();

if (ans == null || ans == trailer)

throw new Exception("No such node");

return ans;

}

public DNode getPrev(DNode v) throws Exception {

DNode ans = v.getPrev();

if (ans == null || ans == header)

throw new Exception("No such node");

return ans;

}

// methods to change the list

public void addBefore(T d, DNode v) {

DNode u = v.getPrev();

DNode x = new DNode(d, u, v);

u.setNext(x);

v.setPrev(x);

size++;

}

public void addAfter(T d, DNode v) {

DNode w = v.getNext();

DNode x = new DNode(d, v, w);

v.setNext(x);

w.setPrev(x);

size++;

}

public void addFirst(T d) {

addAfter(d, header);

}

public void addLast(T d) {

addBefore(d, trailer);

}

public T remove(DNode v) throws Exception {

if (v == header || v == trailer)

throw new Exception("Sentinel");

DNode u = v.getPrev();

DNode w = v.getNext();

w.setPrev(u);

u.setNext(w);

size--;

return v.getData();

}

// LinkedList testing methods:

public String toString() {

String ans = "";

DNode n = header;

ans += "(H)<-->";

do {

n = n.getNext();

if (n == trailer)

ans += "(T)";

else

ans += (n.getData() + "<-->");

} while (n != trailer);

return ans;

}

}

class Term {

Double coefficient;

int degree;

public Term() {

this(null, 0);

}

public boolean isPositive() {

return coefficient > 0;

}

public Term(Double coefficient, int degree) {

this.coefficient = coefficient;

this.degree = degree;

}

public Double getCoefficient() {

return coefficient;

}

public void setCoefficient(Double coefficient) {

this.coefficient = coefficient;

}

public int getDegree() {

return degree;

}

public void setDegree(int degree) {

this.degree = degree;

}

public String toString() {

String ans = "";

if (coefficient.doubleValue() == 0) return "";

if (degree == 0) return coefficient.toString();

if (coefficient != 1) {

if (coefficient == -1) ans += "- ";

else ans += coefficient + " ";

}

ans = ans + "X";

if (degree == 1) return ans;

return ans + "^" + degree;

}

}

abstract class Polynomial {

DList data = null;

public Polynomial() {

data = new DList<>();

}

public final String toString() {

String ans = "";

boolean starting = true;

try {

DNode n = data.getFirst();

while (n != null) {

if (!starting && n.getData().isPositive()) ans += " +";

starting = false;

ans += " " + n.getData().toString();

n = data.getNext(n);

}

} catch (Exception e) {

if (starting) return "0";

}

return ans;

}

abstract public Polynomial add(Polynomial p);

abstract public Polynomial subtract(Polynomial p);

abstract public Polynomial multiply(Polynomial p);

abstract public Polynomial divide(Polynomial p) throws Exception;

abstract public Polynomial remainder(Polynomial p) throws Exception;

}

class Utility {

public static void run(Polynomial p, Polynomial q) throws Exception {

System.out.println("Polynomials p = " + p + " q = " + q);

System.out.println("Sum " + p.add(q));

System.out.println("Difference " + p.subtract(q));

System.out.println("Product " + p.multiply(q));

System.out.println("Quotient " + p.divide(q));

System.out.println("Remainder " + p.remainder(q));

}

}

public class X00000000 extends Polynomial {

public static void main(String args[]) throws Exception {

Polynomial p = new X00000000(" X^5"),

q = new X00000000("X^2 - X + 1");

Utility.run(p, q);

}

public X00000000(String s) {

//parse string character by character

double coef = 0; //coefficient of term

int deg = 0; //degree of term

String[] terms = s.split(" ");

for(int i = 0; i < terms.length; i++)

{

String term= terms[i];

//System.out.println("term:"+term);

String prevTerm="";

if(i != 0)

prevTerm=terms[i-1];

if(term.startsWith("X"))

{

if(term.length()==3 && term.contains("^"))

{

coef=1;

deg=Integer.parseInt(term.substring(2));

}

else if (term.length() == 1)

{

deg=1;

if(prevTerm.equals("-"))

coef=-1;

else

coef=1;

}

}

else if(term.startsWith("-") || term.startsWith("+"))

continue;

else if(term.length()==1 && Character.isDigit(term.charAt(0)))

{

coef=Integer.parseInt(term);

if(prevTerm.equals("-"))

coef*=-1;

deg=0;

}

Term T = new Term(coef, deg);

if(data.isEmpty())

{

data.addFirst(T);

}

else

{

data.addLast(T);

}

}

}

public X00000000() {

super();}

public Polynomial add(Polynomial p) {

Polynomial ans = new X00000000();

// complete this code

return ans;

}

public Polynomial subtract(Polynomial p) {

Polynomial ans = new X00000000();

// complete this code

return ans;

}

public Polynomial multiply(Polynomial p) {

Polynomial ans = new X00000000();

// complete this code

return ans;

}

public Polynomial divide(Polynomial p) throws Exception {

Polynomial ans = new X00000000();

// complete this code

return ans;

}

public Polynomial remainder(Polynomial p) throws Exception {

Polynomial ans = new X00000000();

// complete this code

return ans;

}

}

Actual Output:

Polynomials p = + X^5 q = X^2 - X + 1.0 Sum 0 Difference 0 Product 0 Quotient 0 Remainder 0