LinkedList.java

public class LinkedList<E> {
	
	private class Node{
	public E e;
	public Node next;
	public Node(E e,Node next) {
	this.e=e;
	this.next=next;
	}
	public Node(E e) {
		this(e,null);
	}
	public Node() {
		this(null,null);
	}
  #@Override是代码重构的意思
	@Override
	public String toString() {
		return e.toString();
	}
	}
	private Node dummyHead;
	private int size;
	public LinkedList() {
		dummyHead = new Node(null,null);
		size=0;
	}
	public int getSize() {
		return size;
	}
	public boolean isEmpty() {
		return size==0;
	}
	
	public void add(int index,E e) {
		if(index<0||index>size) {
			throw new IllegalArgumentException("add failed illegal index");
		}
//		if(index==0) {
//			addFrist(e);
//		}else {
//			Node prev=head;
			Node prev=dummyHead;
			for(int i=0;i<index;i++) {
				prev=prev.next;
			}
			prev.next=new Node(e,prev.next);
			size++;
		}
	public void addFirst(E e) {
//		Node node =new Node();
//		node.next=head;
//		head=node;
//		head=new Node(e,head);
//		size++;
		add(0,e);
	}
	public void addLast(E e) {
		add(size,e);
	}
	public E get(int index) {
		if(index<0||index>=size) {
			throw new IllegalArgumentException("add failed illegal index");
		}
		Node cur=dummyHead.next;
		for(int i=0;i<index;i++) {
			cur=cur.next;
		}
		return cur.e;
	}
	public E getFirst() {
		return get(0);
	}
	public E getLast() {
		return get(size-1);
	}
	public void set(int index,E e) {
		if(index<0||index>=size) {
			throw new IllegalArgumentException("add failed illegal index");
		}
		Node cur=dummyHead.next;
		for(int i=0;i<index;i++) {
			cur=cur.next;
		}
		cur.e=e;
	}
	public boolean contains(E e) {
		Node cur=dummyHead.next;
		while(cur!=null) {
			if(cur.e.equals(e)) {
				return true;
			}
			cur=cur.next;
		}
		return false;
	}
	@Override
	public String toString() {
		StringBuilder res=new StringBuilder();
//		Node cur=dummyHead.next;
//		while(cur!=null) {
//			res.append(cur+"->");
//			cur=cur.next;
//		}
		for(Node cur =dummyHead.next;cur!=null;cur=cur.next) {
			res.append(cur+"->");
		}
		res.append("null");
		return res.toString();
	}
	public E remove(int index) {
		if(index<0||index>=size) {
			throw new IllegalArgumentException("remove failed illegal index");
		}
		Node prev=dummyHead;
		for(int i=0;i<index;i++) {
			prev=prev.next;
		}
		Node retNode=prev.next;
		prev.next=retNode.next;
		retNode.next=null;
		size--;
		return retNode.e;
	}
	public E removeFirst() {
		return remove(0);
	}
	public E removeLast() {
		return remove(size-1);
	}
	public void removeElements(E e) {
		Node prev=dummyHead;
		while(prev.next!=null) {
			if(prev.next.e.equals(e)) {
				break;
			}
			prev=prev.next;
		}
		if(prev.next!=null) {
			Node delNode=prev.next;
			prev.next=delNode.next;
			delNode.next=null;
		}
	}
}