LinkedList.java

package com.dataStructure;

public class LinkedList implements List {

	private Node head;
	private Node now;
	

	private int size = 0;

	public void add(Object o) {
		if (head == null) {
			head = new Node(o, null);
			now = head;
		} else {

			Node node = new Node(o, null);
			now.next = node;
			now = node;
		}
		size++;

	}

	private void rangeCheck(int index) {
		if (index < 0 || index > size - 1)
			throw new IllegalArgumentException();
	}

	public void add(int index, Object o) {
		rangeCheck(index);

		if (index == 0) {
			addFirst(o);
		} else {
			Node node = new Node(o, null);
			Node now = head;
			Node next = head;
			for (int i = 1; i <= index; i++) {
				next = next.next;
				if (i == index) {
					node.next = next;
					now.next = node;
				}
				now = now.next;
			}
			size++;
		}
	}

	public Object get(int index) {
		Node indexNode = head;
		if (index == 0)
			return indexNode.data;
		else {

			for (int i = 1; i <= index; i++) {
				indexNode = indexNode.next;
				if (i == index)
					return indexNode.data;
			}
		}
		return null;
	}

	public Object remove(int index) {
		rangeCheck(index);

		if (index == 0) {
			return removeFirst();
		} else {
			Node pre = head;
			Node now = head;
			for (int i = 1; i <= index; i++) {
				now = now.next;
				if (i == index) {
					pre.next = now.next;
				}
				pre = pre.next;
			}
			size--;
			return now.data;
		}
	}

	public int size() {
		return size;
	}

	public boolean isEmpty() {
		return size == 0;
	}

	public void addFirst(Object o) {
		Node oldhead = head;
		Node newhead = new Node(o, oldhead);
		head = newhead;
		size++;
	}

	public void addLast(Object o) {
		if(head==null){
			addFirst(o);
		}else {
			Node node = head;
			while (node != null) {
				node = node.next;
				if (node == null) {
					Node lastnode = new Node(o, null);
					node = lastnode;
				}
			}
			size++;
		}
	}

	public Object removeFirst() {
		Node oldhead = head;
		Node newhead = head.next;
		head = newhead;
		size--;
		return oldhead.data;
	}

	public Object removeLast() {
		if(size == 1){
			Node first = head;
			Object data = first.data;
			head = null;
			size--;
			return data;
		}else{
			Node lastPre = getNode(size-2);
			Node last = lastPre.next;
			Object data = last.data;
			lastPre.next = null;
			size--;
			return data;
		}

	}

	private Node getNode(int index) {
		rangeCheck(index);
		Node cur = head;
		int i = 0;
		while(i <=index){
			cur = cur.next;
			i++;
		}
		return cur;
	}

	public Iterator iterator() {
		return new LinkedListIterator();
	}

	private class LinkedListIterator implements Iterator {
		int pos = 0;

		@Override
		public boolean hasNext() {
			return pos < size;
		}

		@Override
		public Object next() {
			if (pos > size)
				throw new IllegalArgumentException();
			return get(pos++);
		}
	}

	private static class Node {
		Object data;
		Node next;

		private Node(Object data, Node next) {
			this.data = data;
			this.next = next;

		}

	}

}