I implemented a priority queue with linked list like this,when for first time I make an object from seller class and add it to priority queue, it works, but when I make second object from seller to add it to priority queue,it gives an error, I know that my comparator makes this error, but I don't know, how can I compare objects, please help me!
import java.util.Comparator;
public class PQueueTest {
public static void main(String [] args) {
DefaultComparator<Seller> o = new DefaultComparator<>();
Seller s = new Seller("ali", 125, 200);
Seller s1 = new Seller("hasan", 50, 100);
PriorityQueue<Seller> p = new PriorityQueue<>(o);
p.add(s);
p.add(s1);
System.out.println(p.removeMin());
System.out.println(p.removeMin());
}
}
class Node<E> {
private E element;
private Node<E> next;
public Node(E element, Node<E> next) {
this.element = element;
this.next = next;
}
public void setNext(Node<E> next) {
this.next = next;
}
public void setElement(E element) {
this.element = element;
}
public Node<E> getNext() {
return next;
}
public E getElement() {
return element;
}
}
class DefaultComparator<E> implements Comparator<E> {
@Override
public int compare(E a, E b) {
return ((Comparable<E>) a).compareTo(b);
}
}
class PriorityQueue<E> {
private int size;
private Node<E> front;
private DefaultComparator<E> c;
public PriorityQueue(Comparator<? super E> o) {
size = 0;
front = null;
c = (DefaultComparator<E>) o;
}
public boolean isEmpty() {
return size == 0;
}
public int size() {
return size;
}
public void add(E element) {
Node<E> v = new Node<>(element, null);
if (isEmpty()) {
front = v;
}
if (size >= 1) {
Node<E> temp = front;
int comp = c.compare(element, temp.getElement());
while (comp >= 0 && temp.getNext() != null) {
temp = temp.getNext();
comp = c.compare(element, temp.getElement());
}
if (comp < 0) {
// E x = temp.getElement();
v.setNext(temp);
if (temp == front)
front = v;
else {
Node<E> tmp = front;
while (tmp.getNext() != temp) {
tmp = tmp.getNext();
}
tmp.setNext(v);
}
}
if (comp >= 0)
temp.setNext(v);
}
size++;
}
public E removeMin() {
E remove = front.getElement();
front = front.getNext();
size--;
return remove;
}
public E removeMax() {
Node<E> tmp = front;
while (tmp.getNext().getNext() != null) {
tmp = tmp.getNext();
}
E remove = tmp.getNext().getElement();
tmp.setNext(null);
size--;
return remove;
}
public E peekMin() {
E remove = front.getElement();
return remove;
}
public E peekMax() {
Node<E> tmp = front;
while (tmp.getNext().getNext() != null) {
tmp = tmp.getNext();
}
E remove = tmp.getNext().getElement();
return remove;
}
}
class Seller {
private String name;
private long price;
private int stock;
public Seller(String name, long price, int stock) {
this.name = name;
this.price = price;
this.stock = stock;
}
public void setName(String name) {
this.name = name;
}
public void setPrice(long price) {
this.price = price;
}
public void setStock(int stock) {
this.stock = stock;
}
public String getName() {
return name;
}
public long getPrice() {
return price;
}
public int getStock() {
return stock;
}
}
class Buyer {
private String name;
private long price;
private int stock;
public Buyer(String name, long price, int stock) {
this.name = name;
this.price = price;
this.stock = stock;
}
public void setName(String name) {
this.name = name;
}
public void setPrice(long price) {
this.price = price;
}
public void setStock(int stock) {
this.stock = stock;
}
public String getName() {
return name;
}
public long getPrice() {
return price;
}
public int getStock() {
return stock;
}
}
