structure
Class DoublyLinkedList

java.lang.Object
  structure.AbstractStructure
      structure.AbstractList
          structure.DoublyLinkedList

All Implemented Interfaces:

List, Structure

public class DoublyLinkedList
extends AbstractList

An implementation of lists that makes use of doubly linked elements. This provided efficient implementation of both head and tail operations.

Field Summary

protected int	count Number of elements within list.
protected DoublyLinkedNode	head Reference to head of list.
protected DoublyLinkedNode	tail Reference to tail of list.

Constructor Summary

DoublyLinkedList()
Constructs an empty list.

Method Summary

void	add(int i, java.lang.Object o) Insert value at location.
void	add(java.lang.Object value) Add a value to head of list.
void	addFirst(java.lang.Object value) Add a value to head of list.
void	addLast(java.lang.Object value) Add a value to tail of list.
void	clear() Remove all values from list.
boolean	contains(java.lang.Object value) Check to see if a value is within list.
java.lang.Object	get(int i) Get value at location i.
java.lang.Object	getFirst() Get a copy of first value found in list.
java.lang.Object	getLast() Get a copy of last value found in list.
int	indexOf(java.lang.Object value) Determine first location of a value in list.
boolean	isEmpty() Determine if list is empty.
java.util.Iterator	iterator() Construct an iterator to traverse list.
int	lastIndexOf(java.lang.Object value) Determine last location of a value in list.
java.lang.Object	remove(int i) Remove and return value at location i.
java.lang.Object	remove(java.lang.Object value) Remove a value from list.
java.lang.Object	removeFirst() Remove a value from head of list.
java.lang.Object	removeLast() Remove a value from tail of list.
java.lang.Object	set(int i, java.lang.Object o) Set value stored at location i to object o, returning old value.
int	size() Determine number of elements in list.
java.lang.String	toString() Construct a string representation of list.

Methods inherited from class structure.AbstractList

get, remove

Methods inherited from class structure.AbstractStructure

elements, hashCode, values

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface structure.Structure

elements, values

Field Detail

count

protected int count

Number of elements within list.

head

protected DoublyLinkedNode head

Reference to head of list.

tail

protected DoublyLinkedNode tail

Reference to tail of list.

Constructor Detail

DoublyLinkedList

public DoublyLinkedList()

Constructs an empty list.

Postcondition:

constructs an empty list

Method Detail

add

public void add(java.lang.Object value)

Add a value to head of list.

Specified by:

add in interface List

Specified by:

add in interface Structure

Overrides:

add in class AbstractList

Parameters:

value - value to be added.

See Also:

#addToHead

Postcondition:

adds value to beginning of list

addFirst

public void addFirst(java.lang.Object value)

Add a value to head of list.

Specified by:

addFirst in interface List

Overrides:

addFirst in class AbstractList

Parameters:

value - value to be added.

Precondition:

value is not null

Postcondition:

adds element to head of list

removeFirst

public java.lang.Object removeFirst()

Remove a value from head of list. Value is returned.

Specified by:

removeFirst in interface List

Overrides:

removeFirst in class AbstractList

Returns:

value removed from list.

Precondition:

list is not empty

Postcondition:

removes first value from list

addLast

public void addLast(java.lang.Object value)

Add a value to tail of list.

Specified by:

addLast in interface List

Overrides:

addLast in class AbstractList

Parameters:

value - value to be added.

Precondition:

value is not null

Postcondition:

adds new value to tail of list

removeLast

public java.lang.Object removeLast()

Remove a value from tail of list.

Specified by:

removeLast in interface List

Overrides:

removeLast in class AbstractList

Returns:

value removed from list.

Precondition:

list is not empty

Postcondition:

removes value from tail of list

getFirst

public java.lang.Object getFirst()

Get a copy of first value found in list.

Specified by:

getFirst in interface List

Overrides:

getFirst in class AbstractList

Returns:

A reference to first value in list.

Precondition:

list is not empty

Postcondition:

returns first value in list

getLast

public java.lang.Object getLast()

Get a copy of last value found in list.

Specified by:

getLast in interface List

Overrides:

getLast in class AbstractList

Returns:

A reference to last value in list.

Precondition:

list is not empty

Postcondition:

returns last value in list

contains

public boolean contains(java.lang.Object value)

Check to see if a value is within list.

Specified by:

contains in interface List

Specified by:

contains in interface Structure

Overrides:

contains in class AbstractList

Parameters:

value - A value to be found in list.

Returns:

True if value is in list.

Precondition:

value not null

Postcondition:

returns true iff value is in list

remove

public java.lang.Object remove(java.lang.Object value)

Remove a value from list. At most one value is removed. Any duplicates remain. Because comparison is done with "equals," actual value removed is returned for inspection.

Parameters:

value - value to be removed.

Returns:

value actually removed.

Precondition:

value is not null. List can be empty

Postcondition:

first element matching value is removed from list

size

public int size()

Determine number of elements in list.

Returns:

number of elements found in list.

Postcondition:

returns number of elements in list

isEmpty

public boolean isEmpty()

Determine if list is empty.

Specified by:

isEmpty in interface List

Specified by:

isEmpty in interface Structure

Overrides:

isEmpty in class AbstractList

Returns:

True iff list has no values.

Postcondition:

returns true iff list has no elements

clear

public void clear()

Remove all values from list.

Postcondition:

removes all elements from list

get

public java.lang.Object get(int i)

Get value at location i.

Parameters:

i - position of value to be retrieved.

Returns:

value retrieved from location i (returns null if i invalid)

Precondition:

0 <= i < size()

Postcondition:

returns object found at that location

set

public java.lang.Object set(int i,
                            java.lang.Object o)

Set value stored at location i to object o, returning old value.

Parameters:

i - location of entry to be changed.

o - new value

Returns:

former value of ith entry of list.

Precondition:

0 <= i < size()

Postcondition:

sets ith entry of list to value o, returns old value

add

public void add(int i,
                java.lang.Object o)

Insert value at location.

Parameters:

i - index of this new value

o - value to be stored

Precondition:

0 <= i <= size()

Postcondition:

adds ith entry of list to value o

remove

public java.lang.Object remove(int i)

Remove and return value at location i.

Parameters:

i - position of value to be retrieved.

Returns:

value retrieved from location i (returns null if i invalid)

Precondition:

0 <= i < size()

Postcondition:

removes and returns object found at that location

indexOf

public int indexOf(java.lang.Object value)

Determine first location of a value in list.

Parameters:

value - value sought.

Returns:

index (0 is first element) of value, or -1

Precondition:

value is not null

Postcondition:

returns the (0-origin) index of value, or -1 if value is not found

lastIndexOf

public int lastIndexOf(java.lang.Object value)

Determine last location of a value in list.

Parameters:

value - value sought.

Returns:

index (0 is first element) of value, or -1

Precondition:

value is not null

Postcondition:

returns the (0-origin) index of value, or -1 if value is not found

iterator

public java.util.Iterator iterator()

Construct an iterator to traverse list.

Returns:

An iterator that traverses list from head to tail.

See Also:

AbstractIterator, Iterator, Enumeration, Structure.elements()

Postcondition:

returns iterator that allows traversal of list

toString

public java.lang.String toString()

Construct a string representation of list.

Overrides:

toString in class java.lang.Object

Returns:

A string representing elements of list.

Postcondition:

returns a string representing list