Computer Science/61b/Homework/hw5/list/List.java

This page contains computer code. Unlike all articles on the lensowiki, which are released under the GFDL, this code is released under the GPL.

Copyright 2006, 2007 Paul Borokhov. All rights reserved.

This code is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

The code is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

/* 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();
}