import java.util.*;

public class SList { private SListNode head; // First node in list. private SListNode tail; // last node in list. private int size; // Number of items in list.

public SList() { // Here's how to create an empty list. clear(); } /** * @return the number of items in this list */ public int size() { return size; } /** * Tests if the list contains no element * @return true if the list contains no element */ public boolean isEmpty(){ return (size() == 0); } /** * Removes all of the elements from this list. */ public void clear(){ head = null; tail = null; size = 0; } /** * Adds an item to this list, at the front * @param x any object */ public void addFirst(AnyType x) { head = new SListNode(x, head); if (tail == null) tail = head; size++; } /** * Adds an item to this list, at the end * @param x any object */ public void addLast(AnyType x) { // First case: list is empty if (tail == null){ tail = new SListNode(x); head = tail; } // Second case: list is not empty else{ tail.next = new SListNode(x); tail = tail.next; } size++; } /*addLast without using tail*/ /** * Adds an item to this list, at the end * @param x any object */ /* public void addLast(AnyType x) { if (head == null) head = new SListNode(x); else { SListNode current = head; while (current.next != null) { current = current.next; } current.next = new SListNode(x); } size++; } */ /** * Adds an item to this list, at the end * @param x any object */ public void add(AnyType x) { this.addLast(x); } /** * Adds an item to this list at the specified position * @param x any object * @param index position to insert x * @throws IndexOutOfBoundsException if index is not * between 0 and size() */ public void add(int index, AnyType x) throws IndexOutOfBoundsException { if (index < 0 || index > size()) throw new IndexOutOfBoundsException("add at index: "+index);

// First case: add to the end of list if (index == size()) addLast(x); // Second case: add to index 0 else if (index == 0) addFirst(x); else { // Third case: 0 < index < size SListNode prev = head; int prev_ind = 0; while (prev_ind < index - 1) { prev = prev.next; prev_ind++; } //new node should be inserted after prev and before prev.next SListNode newNode = new SListNode(x, prev.next); prev.next = newNode; size++; } } /** * Returns the item at position index * @param index the index to search in * @return return the data of the item in index * @throws IndexOutOfBoundsException if index is not * between 0 and size() */ public AnyType get(int index) throws IndexOutOfBoundsException { if (index < 0 || index > size()) throw new IndexOutOfBoundsException("get index: "+index); SListNode current = head; int curr_ind = 0; while (curr_ind < index) { current = current.next; curr_ind++; } return current.item; } /** * Returns the index of first item matching x * in this list, or -1 if not found. * @param x any object * @return the index of first item matching x * or -1 if not found. */ public int indexOf(Object x) { SListNode current = head; int curr_ind = 0; while (current != null) { if (x.equals(current.item)) return curr_ind; current = current.next; curr_ind++; } return -1; } /** * Tests if some item is in this list * @param x any object * @return true if this list contains an item equal to x */ public boolean contains(Object x) { return indexOf(x) != -1; } /** * Removes an item from this list * @param index the index of the object * @return the item that was removed from the list * @throws IndexOutOfBoundsException if the index is out of range */ public AnyType remove(int index) throws IndexOutOfBoundsException { if (index < 0 || index >= size()) throw new IndexOutOfBoundsException("remove index: "+index); // First case: if list has one element if (size() == 1) { AnyType item = head.item; clear(); return item; } // Second case: remove the index 0 if (index == 0) { AnyType item = head.item; head = head.next; size--; return item; } // Third case: index > 0 SListNode prev = head; int prev_ind = 0; while (prev_ind < index - 1) { prev = prev.next; prev_ind++; } //prev.next is the node that should be removed! AnyType item = prev.next.item; //update the tail, in case prev.next is tail! if (prev.next == tail) tail = prev; prev.next = prev.next.next; size--; return item; } /** * Removes and returns the first element from this list. * @return the first element of the list * @throws NoSuchElementException if list is empty */ public AnyType removeFirst() throws NoSuchElementException { if (isEmpty()) throw new NoSuchElementException("Try to remove the first element of an empty list");

AnyType x = head.item; head = head.next; //update tail, in case there was only one item if (head == null) tail = null; size--; return x; //we can also call remove(0), the time complexity will be the same, O(1) //return remove(0); } /** * Removes and returns the last element from this list. * @return the last element of the list * @throws NoSuchElementException if list is empty */ public AnyType removeLast() throws NoSuchElementException { if (isEmpty()) throw new NoSuchElementException("Try to remove the last element of an empty list"); return remove(size()-1); } /** * Removes the first occurrence of the specified element from this list, * if it is present. If this list does not contain the element, * it is unchanged. * @param x any object that should be removed from the list * @return true if this list contained the specified element, * otherwise return false */ public boolean remove(AnyType x) { // Put your code here } public String toString() { // Put your code here! }

public static void main( String [ ] args ) { SList groceryList = new SList(); groceryList.add(0, "milk"); groceryList.add(0, "bread"); groceryList.add(0, "cheese"); groceryList.add(0, "fruit"); System.out.println("The size of list is: "+groceryList.size()); groceryList.remove(1); System.out.println("List was updated, the size is: "+groceryList.size()); System.out.println("index 1 is: "+groceryList.get(1)); System.out.println("The whole list is: "+ groceryList); // the output should look like this: The whole list is: [ fruit bread milk ] System.out.println("index of value 5 is: "+groceryList.indexOf(5)); System.out.println("The grocery list contains 'milk'? "+groceryList.contains("milk")); groceryList.remove(0); System.out.println("The grocery list contains 'milk'? "+groceryList.contains("milk")); groceryList.remove(0); System.out.println("The grocery list contains 'milk'? "+groceryList.contains("milk")); groceryList.remove(0); System.out.println("The grocery list contains 'milk'? "+groceryList.contains("milk")); }

}

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public class SListNode { public AnyType item; public SListNode next; public SListNode(AnyType d, SListNode next) { this.item = d; this.next = next; } public SListNode(AnyType d) { this(d, null); } }

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can you please help me fill out the 2 asked codes