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/* List.java */
package list;
/**
* A List is a mutable list ADT. No implementation is provided.
*
* DO NOT CHANGE THIS FILE.
**/
public abstract class List {
/**
* size is the number of items in the list.
**/
protected int size;
/**
* isEmpty() returns true if this List is empty, false otherwise.
*
* @return true if this List is empty, false otherwise.
*
* Performance: runs in O(1) time.
**/
public boolean isEmpty() {
return size == 0;
}
/**
* length() returns the length of this List.
*
* @return the length of this List.
*
* Performance: runs in O(1) time.
**/
public int length() {
return size;
}
/**
* insertFront() inserts an item at the front of this List.
*
* @param item is the item to be inserted.
**/
public abstract void insertFront(Object item);
/**
* insertBack() inserts an item at the back of this List.
*
* @param item is the item to be inserted.
**/
public abstract void insertBack(Object item);
/**
* front() returns the node at the front of this List. If the List is
* empty, return an "invalid" node--a node with the property that any
* attempt to use it will cause an exception.
*
* @return a ListNode at the front of this List.
*/
public abstract ListNode front();
/**
* back() returns the node at the back of this List. If the List is
* empty, return an "invalid" node--a node with the property that any
* attempt to use it will cause an exception.
*
* @return a ListNode at the back of this List.
*/
public abstract ListNode back();
/**
* toString() returns a String representation of this List.
*
* @return a String representation of this List.
*/
public abstract String toString();
}
/* List.java */
package list;
/**
* A List is a mutable list ADT. No implementation is provided.
*
* DO NOT CHANGE THIS FILE.
**/
public abstract class List {
/**
* size is the number of items in the list.
**/
protected int size;
/**
* isEmpty() returns true if this List is empty, false otherwise.
*
* @return true if this List is empty, false otherwise.
*
* Performance: runs in O(1) time.
**/
public boolean isEmpty() {
return size == 0;
}
/**
* length() returns the length of this List.
*
* @return the length of this List.
*
* Performance: runs in O(1) time.
**/
public int length() {
return size;
}
/**
* insertFront() inserts an item at the front of this List.
*
* @param item is the item to be inserted.
**/
public abstract void insertFront(Object item);
/**
* insertBack() inserts an item at the back of this List.
*
* @param item is the item to be inserted.
**/
public abstract void insertBack(Object item);
/**
* front() returns the node at the front of this List. If the List is
* empty, return an "invalid" node--a node with the property that any
* attempt to use it will cause an exception.
*
* @return a ListNode at the front of this List.
*/
public abstract ListNode front();
/**
* back() returns the node at the back of this List. If the List is
* empty, return an "invalid" node--a node with the property that any
* attempt to use it will cause an exception.
*
* @return a ListNode at the back of this List.
*/
public abstract ListNode back();
/**
* toString() returns a String representation of this List.
*
* @return a String representation of this List.
*/
public abstract String toString();
}
