So i am seriously in need of help from someone or everyone on improving my program and any corrections if needed. I have listed my codes below and i am hoping to receive input, suggestions, corrections, and advice. Please remember, i am new to programming so please for those of you who have experience, do go to hard on me =(.
package data_structures;
import java.util.Iterator;
import java.util.NoSuchElementException;
public class LinkedListDS<E> implements ListADT<E> {
class Node<E> {
E data;
Node<E> next;
}
public Node(E data) {
this.data = data;
next = null;
}
private Node<E> head, tail;
private int currentSize;
public LinkedListDS() {
head = tail = null;
currentSize = 0;
}
public void addFirst(E obj) {
if(head == null)
head = tail = newNode;
else
newNode.next = head;
head = newNode;
currentSize++;
}
// Adds the Object obj to the end of the list
public void addLast(E o) {
if(head == null)
head = newNode;
tail = newNode;
currentSize++;
return;
{
tail.next = newNode;
tail = newNode;
currentSize++;
}
}
// Removes the first Object in the list and returns it.
// Returns null if the list is empty.
public E removeFirst() {
if(head == null)
return null;
E tmp = head.data;
head = head.next;
{
if (head == null)
tail = null;
currentSize++;
return tmp;
}
}
// Removes the last Object in the list and returns it.
// Returns null if the list is empty.
public E removeLast() {
Node<E> previous = null;
Node<E> current = head;
if (current == null)
return null;
while(current.next != null) {
previous = current;
current = current.next;
}
if(previous = null)
return removeFirst;
previous.next = null;
tail = previous;
currentSize--;
return current.data;
}
// Returns the first Object in the list, but does not remove it.
// Returns null if the list is empty.
public E peekFirst() {
if(head == null)
return null;
return head.data;
}
// Returns the last Object in the list, but does not remove it.
// Returns null if the list is empty.
public E peekLast() {
if(tail == null)
return null;
return tail.data;
}
// Removes the specific Object obj from the list, if it exists.
// Returns true if the Object obj was found and removed, otherwise false
public boolean remove(E obj) {
if(head == null)
return false;
{
if(head.data.equals(obj))
head = head.next;
return true;
}
Node<E> current = head;
while(current.next != null)
{
if(current.next.data.equals(obj))
{
current.next = current.next.next;
return true;
}
current = current.next;
}
currentSize--;
return false,
}
// The list is returned to an empty state.
public void makeEmpty() {
head = tail = null;
currentSize = 0;
}
// Returns true if the list contains the Object obj, otherwise false
public boolean contains(E obj) {
Node<E> current = head;
while(current != null)
{
if(current.data.equals(obj)
return true;
}
current = current.next;
return false;
}
// Returns true if the list is empty, otherwise false
public boolean isEmpty() {
return = null;
}
// Returns true if the list is full, otherwise false
public boolean isFull() {
return false;
}
public int size() { return currentSize; }
public iterator<E> iterator() { return new iterator; }
class IteratorHelper implements Iterator<E> {
Node<E> iteratorPointer;
public IteratorHelper() {
iteratorPointer = head;
}
public boolean hasNext() {
return iteratorPointer != null;
}
public E next() {
if(!hasNext())
throw new NoSuchElementException();
E tmp = iteratorPointer.data;
iteratorPointer = iteratorPointer.next;
return tmp;
}
public void remove() {
throw new UnsupportedOperationException();
}
}
The code below is a Stack Method that i created to go with my LinkedList method, wondering what i might do in order to make it better, what i might/should consider to take out or add. I receive compiler errors as well with this code:
package data_structures;
import java.util.Iterator;
public class Stack<E> implements Iterable<E> {
private ListADT<E> list;
public Stack() {
list = new LinkedListDS<E>( );
}
public void push(E obj) {
list.addFirst(obj);
}
public E pop() {
return list.removeFirst();
}
public int size() {}
public boolean isEmpty() {}
public boolean isFull() {}
public E peek() {}
public boolean contains(E obj) {}
public void makeEmpty() {}
public Iterator<E> iterator() {
return list.iterator();
}
class IteratorHelper implements Iterator<E> {
Node<E> iteratorPointer;
public IteratorHelper() {
iteratorPointer = head;
}
public boolean hasNext() {
return iteratorPointer != null;
}
public E next() {
if(!hasNext())
throw new NoSuchElementException();
E tmp = iteratorPointer.data;
iteratorPointer = iteratorPointer.next;
return tmp;
}
public void remove() {
throw new UnsupportedOperationException();
}
Now the last method that i have listed below is my Queue method, again looking for advice, input, and correction:
package data_structures;
import java.util.Iterator;
public class Queue<E> implements Iterable<E> {
private ListADT<E> list;
public Queue() {
data = new LinkedList<E>();
}
public void enqueue(E obj) {
data.addLast(value);
}
public E dequeue() {
return data.removeFirst();
}
public int size() {}
public boolean isEmpty() {}
public boolean isFull() {}
public E peek() {}
public boolean contains(E obj) {}
public void makeEmpty() {}
public Iterator<E> iterator() {
return data.iterator();
}
class IteratorHelper implements Iterator<E> {
Node<E> iteratorPointer;
public IteratorHelper() {
iteratorPointer = head;
}
public boolean hasNext() {
return iteratorPointer != null;
}
public E next() {
if(!hasNext())
throw new NoSuchElementException();
E tmp = iteratorPointer.data;
iteratorPointer = iteratorPointer.next;
return tmp;
}
public void remove() {
throw new UnsupportedOperationException();
}
}
