I hope that someone can help me with my little problem. I defined my EmptyQueue and my NotEmptyQueue in this way, following my interface Immutable queue. The main problem it's that the method enQueue, that should add an element to myQueue is not working. Pls help me:
Interface:
public interface ImmutableQueue<E> extends Iterable<E> {
boolean isEmpty();
int size();
ImmutableQueue<E> enQueue(E e);
ImmutableQueue<E> deQueue();
E getTop();
}
EmptyQueue:
import java.util.Iterator;
import java.util.NoSuchElementException;
public class EmptyQueue<E> implements ImmutableQueue <E>, Iterable <E> {
@Override
public boolean isEmpty() {
return true;
}
@Override
public int size() {
return 0;
}
@Override
public ImmutableQueue<E> enQueue(E e) {
NotEmptyQueue<E> q= new NotEmptyQueue <>(e,this);
return q;
}
@Override
public ImmutableQueue<E> deQueue() {
throw new NoSuchElementException();
}
@Override
public E getTop() {
throw new NoSuchElementException();
}
@Override
public Iterator<E> iterator() {
return new Iterator<E>(){
@Override
public boolean hasNext() {
return false;
}
@Override
public E next() {
throw new NoSuchElementException();
}
};
}
}
NotEmptyQueue:
import java.util.Iterator;
public class NotEmptyQueue<E> implements ImmutableQueue<E>, Iterable <E>{
public E e;
public ImmutableQueue<E> tail;
public NotEmptyQueue(E e, ImmutableQueue<E> tail){
this.e = e;
this.tail = tail;
}
@Override
public boolean isEmpty() {
return false;
}
@Override
public int size() {
return tail.size() + 1;
}
@Override
public ImmutableQueue<E> enQueue(E e) {
return new NotEmptyQueue<>(e,this);
}
@Override
public ImmutableQueue<E> deQueue() {
return tail;
}
@Override
public E getTop(){
return e;
}
public static void main (String [] args){
NotEmptyQueue<Integer> myQueue= new NotEmptyQueue<>(new Integer(1),null);
myQueue.enQueue(9);
myQueue.enQueue(7);
System.out.println(myQueue.size());
System.out.println(myQueue.getTop());
for(Integer i : myQueue){
System.out.println(i);
}
}
@Override
public Iterator<E> iterator() {
return new Iterator<E>(){
ImmutableQueue<E> queue;
@Override
public boolean hasNext() {
return (!tail.isEmpty());
}
@Override
public E next() {
E res = queue.getTop();
queue = queue.deQueue();
return res;
}
Iterator<E> setQueue(ImmutableQueue<E> queue){
this.queue = queue;
return this;
}
}.setQueue(this);
}
}
myQueue.enQueue(9);
should be
myQueue = myQueue.enQueue(9);
That's the usual way to deal with a persistent queue like you have.