LinkedList.java

package ds.linked.singly;

import java.util.Iterator;

public class LinkedList<Item> implements Iterable<Item>{

    Node<Item> head;
    int size = 0;

    /* Add a new item to the beginning of the list */
    public void addToFront(Item item) {
        Node<Item> newNode = new Node<Item>();  // 1
        newNode.data = item;                    // 1
        newNode.next = head;                    // 2
        head = newNode;                         // 3
        size++;                                 // 4
    }

    /* Remove an item from the beginning of the list */
    public void removeFromFront() {
        if (head == null) {                                                     // 1
            throw new IndexOutOfBoundsException("The linked list is empty.");   // 1
        }                                                                       // 1
        head = head.next;                                                       // 2
        size--;                                                                 // 3
    }

    /* Add a new item to the end of the list */
    public void addToRear(Item item) {
        Node<Item> newNode = new Node<Item>();      // 1
        newNode.data = item;                        // 1

        if (head == null) {                         // 2
            head = newNode;                         // 2
        } else {
            Node<Item> current = head;              // 3
            while (current.next != null) {          // 4
                current = current.next;             // 4
            }                                       // 4
            current.next = newNode;                 // 5
        }
        size++;                                     // 6
    }

    /* Remove an item from the end of the list */
    public void removeFromRear() {
        if (head == null) {                                                     // 1
            throw new IndexOutOfBoundsException("The linked list is empty.");   // 1
        } else if (size == 1) {                                                 // 2
            head = null;                                                        // 2
        } else {                                                                // 3
            Node<Item> current = head;                                          // 3
            while (current.next.next != null) {                                 // 4
                current = current.next;                                         // 4
            }                                                                   // 4
            current.next = null;                                                // 5
        }
        size--;                                                                 // 6
    }

    /* Return the size of the linked list */
    public int count() {
        return size;
    }

    /* Return an Iterator Object */
    public Iterator<Item> iterator() {
        return new LinkedListIterator();
    }

    /* Define the Iterator class, and hasNext() and next() methods */
    private class LinkedListIterator implements Iterator<Item> {        // 1
        Node<Item> current = head;                                      // 2

        public boolean hasNext() {                                      // 3
            return current != null;                                     // 3
        }                                                               // 3

        public Item next() {                                            // 4
            Item item = current.data;                                   // 4
            current = current.next;                                     // 4
            return item;                                                // 4
        }
    }

}