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‎UCB CS61B/Homework and Projects/project/pj2/list/DList.java

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/* DList.java */
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package com.cs61b.project2.list;
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/**
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* A DList is a mutable doubly-linked list ADT. Its implementation is
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* circularly-linked and employs a sentinel node at the head of the list.
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*
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* DO NOT CHANGE ANY METHOD PROTOTYPES IN THIS FILE.
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**/
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public class DList extends List {
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/**
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* (inherited) size is the number of items in the list.
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* head references the sentinel node.
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* Note that the sentinel node does not store an item, and is not included
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* in the count stored by the "size" field.
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*
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* DO NOT CHANGE THE FOLLOWING FIELD DECLARATION.
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**/
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protected DListNode head;
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/* DList invariants:
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* 1) head != null.
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* 2) For every DListNode x in a DList, x.next != null.
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* 3) For every DListNode x in a DList, x.prev != null.
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* 4) For every DListNode x in a DList, if x.next == y, then y.prev == x.
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* 5) For every DListNode x in a DList, if x.prev == y, then y.next == x.
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* 6) For every DList l, l.head.myList = null. (Note that l.head is the
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* sentinel.)
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* 7) For every DListNode x in a DList l EXCEPT l.head (the sentinel),
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* x.myList = l.
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* 8) size is the number of DListNodes, NOT COUNTING the sentinel,
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* that can be accessed from the sentinel (head) by a sequence of
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* "next" references.
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**/
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/**
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* newNode() calls the DListNode constructor. Use this method to allocate
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* new DListNodes rather than calling the DListNode constructor directly.
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* That way, only this method need be overridden if a subclass of DList
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* wants to use a different kind of node.
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*
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* @param item the item to store in the node.
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* @param list the list that owns this node. (null for sentinels.)
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* @param prev the node previous to this node.
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* @param next the node following this node.
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**/
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protected DListNode newNode(Object item, DList list, DListNode prev, DListNode next)
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{
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return new DListNode(item, list, prev, next);
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}
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/**
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* DList() constructs for an empty DList.
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**/
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public DList()
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{
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// Your solution here. Similar to Homework 4, but now you need to
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// specify
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// the `list' field (second parameter) as well.
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head = newNode(Integer.MIN_VALUE, null, null, null);
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head.next = head;
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head.prev = head;
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size = 0;
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}
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/**
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* insertFront() inserts an item at the front of this DList.
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*
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* @param item is the item to be inserted.
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*
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* Performance: runs in O(1) time.
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**/
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public void insertFront(Object item)
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{
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// Your solution here. Similar to Homework 4, but now you need to
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// specify
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// the `list' field (second parameter) as well.
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DListNode front = newNode(item, this, head, head.next);
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head.next.prev = front;
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head.next = front;
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size++;
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}
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/**
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* insertBack() inserts an item at the back of this DList.
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*
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* @param item is the item to be inserted.
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*
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* Performance: runs in O(1) time.
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**/
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public void insertBack(Object item)
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{
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// Your solution here. Similar to Homework 4, but now you need to
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// specify
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// the `list' field (second parameter) as well.
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DListNode back = newNode(item, this, head.prev, head);
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head.prev.next = back;
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head.prev = back;
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size++;
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}
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/**
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* front() returns the node at the front of this DList. If the DList is
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* empty, return an "invalid" node--a node with the property that any
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* attempt to use it will cause an exception. (The sentinel is "invalid".)
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*
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* DO NOT CHANGE THIS METHOD.
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*
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* @return a ListNode at the front of this DList.
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*
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* Performance: runs in O(1) time.
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*/
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public ListNode front()
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{
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return head.next;
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}
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/**
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* back() returns the node at the back of this DList. If the DList is
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* empty, return an "invalid" node--a node with the property that any
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* attempt to use it will cause an exception. (The sentinel is "invalid".)
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*
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* DO NOT CHANGE THIS METHOD.
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*
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* @return a ListNode at the back of this DList.
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*
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* Performance: runs in O(1) time.
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*/
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public ListNode back()
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{
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return head.prev;
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}
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/**
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* toString() returns a String representation of this DList.
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*
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* DO NOT CHANGE THIS METHOD.
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*
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* @return a String representation of this DList.
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*
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* Performance: runs in O(n) time, where n is the length of the list.
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*/
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public String toString()
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{
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String result = "[ ";
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DListNode current = head.next;
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while (current != head)
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{
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result = result + current.item + " ";
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current = current.next;
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}
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return result + "]";
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}
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public void remove(DListNode node)
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{
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node.prev.next = node.next;
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node.next.prev = node.prev;
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node.prev = null;
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node.next = null;
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size--;
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}
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public DListNode find(Object item) throws InvalidNodeException
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{
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DListNode cur = head.next;
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while(cur != null)
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{
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if(cur.item() == item)
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{
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return cur;
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}
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cur = cur.next;
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}
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return null;
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}
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private static void testInvalidNode(ListNode p)
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{
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System.out.println("p.isValidNode() should be false: " + p.isValidNode());
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try
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{
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p.item();
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System.out.println("p.item() should throw an exception, but didn't.");
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}
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catch (InvalidNodeException lbe)
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{
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System.out.println("p.item() should throw an exception, and did.");
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}
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try
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{
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p.setItem(new Integer(0));
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System.out.println("p.setItem() should throw an exception, but didn't.");
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}
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catch (InvalidNodeException lbe)
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{
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System.out.println("p.setItem() should throw an exception, and did.");
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}
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try
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{
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p.next();
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System.out.println("p.next() should throw an exception, but didn't.");
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}
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catch (InvalidNodeException lbe)
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{
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System.out.println("p.next() should throw an exception, and did.");
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}
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try
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{
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p.prev();
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System.out.println("p.prev() should throw an exception, but didn't.");
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}
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catch (InvalidNodeException lbe)
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{
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System.out.println("p.prev() should throw an exception, and did.");
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}
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try
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{
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p.insertBefore(new Integer(1));
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System.out.println("p.insertBefore() should throw an exception, but " + "didn't.");
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}
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catch (InvalidNodeException lbe)
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{
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System.out.println("p.insertBefore() should throw an exception, and did.");
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}
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try
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{
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p.insertAfter(new Integer(1));
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System.out.println("p.insertAfter() should throw an exception, but " + "didn't.");
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}
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catch (InvalidNodeException lbe)
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{
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System.out.println("p.insertAfter() should throw an exception, and did.");
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}
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try
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{
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p.remove();
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System.out.println("p.remove() should throw an exception, but didn't.");
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}
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catch (InvalidNodeException lbe)
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{
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System.out.println("p.remove() should throw an exception, and did.");
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}
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}
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private static void testEmpty()
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{
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List l = new DList();
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System.out.println("An empty list should be [ ]: " + l);
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System.out.println("l.isEmpty() should be true: " + l.isEmpty());
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System.out.println("l.length() should be 0: " + l.length());
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System.out.println("Finding front node p of l.");
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ListNode p = l.front();
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testInvalidNode(p);
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System.out.println("Finding back node p of l.");
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p = l.back();
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testInvalidNode(p);
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l.insertFront(new Integer(10));
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System.out.println("l after insertFront(10) should be [ 10 ]: " + l);
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}
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public static void main(String[] argv)
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{
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testEmpty();
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List l = new DList();
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l.insertFront(new Integer(3));
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l.insertFront(new Integer(2));
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l.insertFront(new Integer(1));
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System.out.println("l is a list of 3 elements: " + l);
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try
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{
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ListNode n;
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int i = 1;
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for (n = l.front(); n.isValidNode(); n = n.next())
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{
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System.out.println("n.item() should be " + i + ": " + n.item());
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n.setItem(new Integer(((Integer) n.item()).intValue() * 2));
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System.out.println("n.item() should be " + 2 * i + ": " + n.item());
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i++;
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}
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System.out.println("After doubling all elements of l: " + l);
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testInvalidNode(n);
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i = 6;
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for (n = l.back(); n.isValidNode(); n = n.prev())
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{
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System.out.println("n.item() should be " + i + ": " + n.item());
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n.setItem(new Integer(((Integer) n.item()).intValue() * 2));
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System.out.println("n.item() should be " + 2 * i + ": " + n.item());
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i = i - 2;
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}
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System.out.println("After doubling all elements of l again: " + l);
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testInvalidNode(n);
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n = l.front().next();
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System.out.println("Removing middle element (8) of l: " + n.item());
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n.remove();
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System.out.println("l is now: " + l);
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testInvalidNode(n);
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n = l.back();
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System.out.println("Removing end element (12) of l: " + n.item());
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n.remove();
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System.out.println("l is now: " + l);
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testInvalidNode(n);
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n = l.front();
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System.out.println("Removing first element (4) of l: " + n.item());
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n.remove();
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System.out.println("l is now: " + l);
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testInvalidNode(n);
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}
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catch (InvalidNodeException lbe)
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{
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System.err.println("Caught InvalidNodeException that should not happen.");
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System.err.println("Aborting the testing code.");
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}
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}
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}

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