Thread: Linked Lists

Hi, i keep getting an error saying that NaN might not have been initialized. I think its because there is something else is wrong with my code, but i am not sure what it is. I just started using linked lists and any help would be really appreciated

import java.lang.Double;
public class LinkedListOfDoubles
{
private DoubleNode head;
private DoubleNode tail;
private int size;
public static final double NaN;
public LinkedListOfDoubles()
{
this.head = null;
this.tail = null;
this.size = 0;
}

public void addFront(double d)
{
if(head == null){
DoubleNode newNode;
newNode = new DoubleNode(d, head, null);

newNode.setNext(head);
head = newNode;
tail = head;
size++;
}else{
DoubleNode newNode;
newNode = new DoubleNode(d, head, null);

newNode.setNext(head);
head = newNode;
size++;
}
}

public void addBack(double d)
{
if(tail == null){
addFront(d);
}else{

DoubleNode newNode;
newNode = new DoubleNode(d, null, tail);
tail.setNext(newNode);
tail = newNode;
size++;
}
}

public void remove(double d)
{
if(size()== 1){
head = null;
tail = null;
size--;
}else if(size > 1){
for(DoubleNode x = head; x.next() != null; x.next())
{
if(x.getItem() == d)
{
x.setItem(x.next().getItem());
size--;
}
}
}
}

public void removeThreshold(double d, double threshold)
{
DoubleNode compare = head;
double d1 = d + threshold;
double d2 = d - threshold;
if(compare.getItem() >= d2 && compare.getItem() <= d1 ){
compare.setItem(compare.next().getItem());
size--;
}
}

public int size()
{
return size;
}

public int withinThreshold(double d, double threshold)
{
int count = 0;
double d1 = d + threshold;
double d2 = d - threshold;
for(DoubleNode compare = head; compare.next() != null; compare = compare.next()){
if(compare.getItem() >= d2 && compare.getItem() <= d1){
count++;
}
compare = compare.next();
}
return count;
}

public double maximum()
{
DoubleNode compare = head;
if(size >= 1){
while(compare.next() != null){
if(compare.next().getItem() > compare.getItem() || compare.next().getItem() == compare.getItem()){
compare = compare.next();
}
}
return compare.getItem();
}else{
return Double.NaN;
}
}

public double minimum()
{
DoubleNode compare = head;
if(size >= 1){
while(compare.next() != null){
if(compare.next().getItem() > compare.getItem() || compare.next ().getItem() == compare.getItem()){
compare = compare.next();
}
}
return compare.getItem();
}else{
return Double.NaN;
}
}

public double mean()
{
if(size() == 0){
return Double.NaN;
}else{
double mean = 0.0;
DoubleNode curr = head;
mean += curr.getItem();
if (size >= 1){
curr = curr.next();
mean += curr.getItem();
}
return (mean / size);
}
}

public double elementAt(int index)
{
DoubleNode temp;
temp = head;
if(index >= 0 && index < size())
{
for(int i =0; i < index; i++)
{
temp = temp.next();
}
return temp.getItem();
}

return Double.NaN;
}

public String toString()
{
DoubleNode curr = head;
String list = "{";
list += curr;
while(curr == null){
list += ", ";
curr = curr.next();
list += curr;
}
list += "}";
return list;
}

}

It's because you have the line:

private static double NaN;

Then the value for that is never set and you start to return that value even though you never set it to anything. Also please use the CODE tags next time