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/* ListNode.java */
package list;
/**
* A ListNode is a mutable node in a list. No implementation is provided.
*
* DO NOT CHANGE THIS FILE.
**/
public abstract class ListNode {
/**
* item references the item stored in the current node.
* myList references the List that contains this node.
*
* DO NOT CHANGE THE FOLLOWING FIELD DECLARATIONS.
*/
protected Object item;
protected List myList;
/**
* isValidNode returns true if this node is valid; false otherwise.
* By default, an invalid node is one that doesn't belong to a list (myList
* is null), but subclasses can override this definition.
*
* @return true if this node is valid; false otherwise.
*
* Performance: runs in O(1) time.
*/
public boolean isValidNode() {
return myList != null;
}
/**
* item() returns this node's item. If this node is invalid,
* throws an exception.
*
* @return the item stored in this node.
*
* Performance: runs in O(1) time.
*/
public Object item() throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException();
}
return item;
}
/**
* setItem() sets this node's item to "item". If this node is invalid,
* throws an exception.
*
* Performance: runs in O(1) time.
*/
public void setItem(Object item) throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException();
}
this.item = item;
}
/**
* 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.
*/
public abstract ListNode next() throws InvalidNodeException;
/**
* 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.
*/
public abstract ListNode prev() throws InvalidNodeException;
/**
* 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.
*/
public abstract void insertAfter(Object item) throws InvalidNodeException;
/**
* 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.
*/
public abstract void insertBefore(Object item) throws InvalidNodeException;
/**
* remove() removes this node from its List. If this node is invalid,
* throws an exception.
*
* @exception InvalidNodeException if this node is not valid.
*/
public abstract void remove() throws InvalidNodeException;
}
/* ListNode.java */
package list;
/**
* A ListNode is a mutable node in a list. No implementation is provided.
*
* DO NOT CHANGE THIS FILE.
**/
public abstract class ListNode {
/**
* item references the item stored in the current node.
* myList references the List that contains this node.
*
* DO NOT CHANGE THE FOLLOWING FIELD DECLARATIONS.
*/
protected Object item;
protected List myList;
/**
* isValidNode returns true if this node is valid; false otherwise.
* By default, an invalid node is one that doesn't belong to a list (myList
* is null), but subclasses can override this definition.
*
* @return true if this node is valid; false otherwise.
*
* Performance: runs in O(1) time.
*/
public boolean isValidNode() {
return myList != null;
}
/**
* item() returns this node's item. If this node is invalid,
* throws an exception.
*
* @return the item stored in this node.
*
* Performance: runs in O(1) time.
*/
public Object item() throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException();
}
return item;
}
/**
* setItem() sets this node's item to "item". If this node is invalid,
* throws an exception.
*
* Performance: runs in O(1) time.
*/
public void setItem(Object item) throws InvalidNodeException {
if (!isValidNode()) {
throw new InvalidNodeException();
}
this.item = item;
}
/**
* 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.
*/
public abstract ListNode next() throws InvalidNodeException;
/**
* 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.
*/
public abstract ListNode prev() throws InvalidNodeException;
/**
* 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.
*/
public abstract void insertAfter(Object item) throws InvalidNodeException;
/**
* 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.
*/
public abstract void insertBefore(Object item) throws InvalidNodeException;
/**
* remove() removes this node from its List. If this node is invalid,
* throws an exception.
*
* @exception InvalidNodeException if this node is not valid.
*/
public abstract void remove() throws InvalidNodeException;
}
