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/* DListNode.java */
package list;
/**
* A DListNode is a mutable node in a DList (doubly-linked list).
**/
public class DListNode extends ListNode {
/**
* (inherited) item references the item stored in the current node.
* (inherited) myList references the List that contains this node.
* prev references the previous node in the DList.
* next references the next node in the DList.
*
* DO NOT CHANGE THE FOLLOWING FIELD DECLARATIONS.
**/
protected DListNode prev;
protected DListNode next;
/**
* DListNode() constructor.
* @param i the item to store in the node.
* @param l the list this node is in.
* @param p the node previous to this node.
* @param n the node following this node.
*/
DListNode(Object i, DList l, DListNode p, DListNode n) {
item = i;
myList = l;
prev = p;
next = n;
}
/**
* isValidNode returns true if this node is valid; false otherwise.
* An invalid node is represented by a `myList' field with the value null.
* Sentinel nodes are invalid, and nodes that don't belong to a list are
* also invalid.
*
* @return true if this node is valid; false otherwise.
*
* Performance: runs in O(1) time.
*/
public boolean isValidNode() {
return myList != null;
}
/**
* next() returns the node following this node. If this node is invalid,
* throws an exception.
*
* @return the node following this node.
* @exception InvalidNodeException if this node is not valid.
*
* Performance: runs in O(1) time.
*/
public ListNode next() throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException("next() called on invalid node");
}
return next;
}
/**
* prev() returns the node preceding this node. If this node is invalid,
* throws an exception.
*
* @param node the node whose predecessor is sought.
* @return the node preceding this node.
* @exception InvalidNodeException if this node is not valid.
*
* Performance: runs in O(1) time.
*/
public ListNode prev() throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException("prev() called on invalid node");
}
return prev;
}
/**
* insertAfter() inserts an item immediately following this node. If this
* node is invalid, throws an exception.
*
* @param item the item to be inserted.
* @exception InvalidNodeException if this node is not valid.
*
* Performance: runs in O(1) time.
*/
public void insertAfter(Object item) throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException("insertAfter() called on invalid node");
}
DListNode insertion = ((DList) myList).newNode(item, (DList) myList, this, this.next);
this.next.prev = insertion;
this.next = insertion;
myList.size++;
}
/**
* insertBefore() inserts an item immediately preceding this node. If this
* node is invalid, throws an exception.
*
* @param item the item to be inserted.
* @exception InvalidNodeException if this node is not valid.
*
* Performance: runs in O(1) time.
*/
public void insertBefore(Object item) throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException("insertBefore() called on invalid node");
}
DListNode insertion = ((DList) myList).newNode(item, (DList) myList, this.prev, this);
this.prev.next = insertion;
this.prev = insertion;
myList.size++;
}
/**
* remove() removes this node from its DList. If this node is invalid,
* throws an exception.
*
* @exception InvalidNodeException if this node is not valid.
*
* Performance: runs in O(1) time.
*/
public void remove() throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException("remove() called on invalid node");
}
// Your solution here. Will look something like your Homework 4 solution,
// but changes are necessary. For instance, there is no need to check if
// "this" is null. Remember that this node's "myList" field tells you
// what DList it's in.
this.prev.next = this.next;
this.next.prev = this.prev;
myList.size--;
// Make this node an invalid node, so it cannot be used to corrupt myList.
myList = null;
// Set other references to null to improve garbage collection.
next = null;
prev = null;
}
}
package list;
/**
* A DListNode is a mutable node in a DList (doubly-linked list).
**/
public class DListNode extends ListNode {
/**
* (inherited) item references the item stored in the current node.
* (inherited) myList references the List that contains this node.
* prev references the previous node in the DList.
* next references the next node in the DList.
*
* DO NOT CHANGE THE FOLLOWING FIELD DECLARATIONS.
**/
protected DListNode prev;
protected DListNode next;
/**
* DListNode() constructor.
* @param i the item to store in the node.
* @param l the list this node is in.
* @param p the node previous to this node.
* @param n the node following this node.
*/
DListNode(Object i, DList l, DListNode p, DListNode n) {
item = i;
myList = l;
prev = p;
next = n;
}
/**
* isValidNode returns true if this node is valid; false otherwise.
* An invalid node is represented by a `myList' field with the value null.
* Sentinel nodes are invalid, and nodes that don't belong to a list are
* also invalid.
*
* @return true if this node is valid; false otherwise.
*
* Performance: runs in O(1) time.
*/
public boolean isValidNode() {
return myList != null;
}
/**
* next() returns the node following this node. If this node is invalid,
* throws an exception.
*
* @return the node following this node.
* @exception InvalidNodeException if this node is not valid.
*
* Performance: runs in O(1) time.
*/
public ListNode next() throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException("next() called on invalid node");
}
return next;
}
/**
* prev() returns the node preceding this node. If this node is invalid,
* throws an exception.
*
* @param node the node whose predecessor is sought.
* @return the node preceding this node.
* @exception InvalidNodeException if this node is not valid.
*
* Performance: runs in O(1) time.
*/
public ListNode prev() throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException("prev() called on invalid node");
}
return prev;
}
/**
* insertAfter() inserts an item immediately following this node. If this
* node is invalid, throws an exception.
*
* @param item the item to be inserted.
* @exception InvalidNodeException if this node is not valid.
*
* Performance: runs in O(1) time.
*/
public void insertAfter(Object item) throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException("insertAfter() called on invalid node");
}
DListNode insertion = ((DList) myList).newNode(item, (DList) myList, this, this.next);
this.next.prev = insertion;
this.next = insertion;
myList.size++;
}
/**
* insertBefore() inserts an item immediately preceding this node. If this
* node is invalid, throws an exception.
*
* @param item the item to be inserted.
* @exception InvalidNodeException if this node is not valid.
*
* Performance: runs in O(1) time.
*/
public void insertBefore(Object item) throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException("insertBefore() called on invalid node");
}
DListNode insertion = ((DList) myList).newNode(item, (DList) myList, this.prev, this);
this.prev.next = insertion;
this.prev = insertion;
myList.size++;
}
/**
* remove() removes this node from its DList. If this node is invalid,
* throws an exception.
*
* @exception InvalidNodeException if this node is not valid.
*
* Performance: runs in O(1) time.
*/
public void remove() throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException("remove() called on invalid node");
}
// Your solution here. Will look something like your Homework 4 solution,
// but changes are necessary. For instance, there is no need to check if
// "this" is null. Remember that this node's "myList" field tells you
// what DList it's in.
this.prev.next = this.next;
this.next.prev = this.prev;
myList.size--;
// Make this node an invalid node, so it cannot be used to corrupt myList.
myList = null;
// Set other references to null to improve garbage collection.
next = null;
prev = null;
}
}
