myhw1

Class InventorySet

java.lang.Object

myhw1.InventorySet

final class InventorySet
extends java.lang.Object

An Inventory implemented using a HashMap<Video,Record>. Keys are Videos; Values are Records.

Class Type: Mutable Collection of Records

Object Invariant:

Every key and value in the map is non-null.

Object Invariant:

Each value r is stored under key r.video.

Field Summary

Fields

Modifier and Type	Field and Description
private java.util.Map<VideoObj,Record>	data Invariant: _data != null

Constructor Summary

Constructors

Constructor and Description
InventorySet()

Method Summary

Modifier and Type	Method and Description
void	addNumOwned(VideoObj video, int change) Add or remove copies of a video from the inventory.
void	checkIn(VideoObj video) Check in a video.
void	checkOut(VideoObj video) Check out a video.
void	clear() Remove all records from the inventory.
Record	get(VideoObj v) Return a copy of the record for a given Video; if not present, return null.
int	size() Return the number of Records.
java.util.Collection<Record>	toCollection() Return a copy of the records as a collection.
java.lang.String	toString() Return the contents of the inventory as a string.

Methods inherited from class java.lang.Object

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

Field Detail

data

private final java.util.Map<VideoObj,Record> data

Invariant: _data != null

Constructor Detail

InventorySet

InventorySet()

Method Detail

size

public int size()

Return the number of Records.

get

public Record get(VideoObj v)

Return a copy of the record for a given Video; if not present, return null.

toCollection

public java.util.Collection<Record> toCollection()

Return a copy of the records as a collection. Neither the underlying collection, nor the actual records are returned.

addNumOwned

public void addNumOwned(VideoObj video,
                        int change)

Add or remove copies of a video from the inventory. If a video record is not already present (and change is positive), a record is created. If a record is already present, numOwned is modified using change. If change brings the number of copies to be zero, the record is removed from the inventory.

Parameters:

video - the video to be added.

change - the number of copies to add (or remove if negative).

Throws:

java.lang.IllegalArgumentException - if video null, change is zero, if attempting to remove more copies than are owned, or if attempting to remove copies that are checked out.

Postcondition: changes the record for the video

checkOut

public void checkOut(VideoObj video)

Check out a video.

Parameters:

video - the video to be checked out.

Throws:

java.lang.IllegalArgumentException - if video has no record or numOut equals numOwned.

Postcondition: changes the record for the video

checkIn

public void checkIn(VideoObj video)

Check in a video.

Parameters:

video - the video to be checked in.

Throws:

java.lang.IllegalArgumentException - if video has no record or numOut non-positive.

Postcondition: changes the record for the video

clear

public void clear()

Remove all records from the inventory.

Postcondition: size() == 0

toString

public java.lang.String toString()

Return the contents of the inventory as a string.

Overrides:

toString in class java.lang.Object