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 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 addFirst(E e){ add(0,e); } public void add(int index,E e){ if (index < 0 || index >size ) throw new IllegalArgumentException("add failed.Illegal index."); Node prev = dummyHead; for(int i = 0; i < index; i++) prev = prev.next; Node node = new Node(e); node.next = prev.next; prev.next = node; size++; } public void addLast(E e){ add(size,e); } public E get(int index){ if(index < 0 || index >= size) throw new IllegalArgumentException("get 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("set 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; }}