edu.colorado.collections
Class ArrayBag<E>

java.lang.Object
  edu.colorado.collections.ArrayBag<E>

All Implemented Interfaces:

java.lang.Cloneable

public class ArrayBag<E>
extends java.lang.Object
implements java.lang.Cloneable

An ArrayBag is a generic collection of references to objects. The same object may appear multiple times in a bag.

See Also:

Java Source Code for this class (www.cs.colorado.edu/~main/edu/colorado/collections/ArrayBag.java) , IntArrayBag, LinkedBag

Note:

(1) The capacity of one of these bags can change after it's created, but the maximum capacity is limited by the amount of free memory on the machine. The constructor, addItem, clone, and union will result in an OutOfMemoryError when free memory is exhausted.

(2) A bag's capacity cannot exceed the maximum integer 2,147,483,647 (Integer.MAX_VALUE). Any attempt to create a larger capacity results in a failure due to an arithmetic overflow.

(3) Because of the slow linear algorithms of this class, large bags will have poor performance.

Constructor Summary

ArrayBag()
Initialize an empty bag with an initial capacity of 10.

ArrayBag(int initialCapacity)
Initialize an empty bag with a specified initial capacity.

Method Summary

void	add(E element) Add a new element to this bag.
void	addAll(ArrayBag<E> addend) Add the contents of another bag to this bag.
void	addMany(E... elements) Add new elements to this bag.
ArrayBag<E>	clone() Generate a copy of this bag.
int	countOccurrences(E target) Accessor method to count the number of occurrences of a particular element in this bag.
void	ensureCapacity(int minimumCapacity) Change the current capacity of this bag.
int	getCapacity() Accessor method to get the current capacity of this bag.
E	grab() Accessor method to retrieve a random element from this bag.
boolean	remove(E target) Remove one copy of a specified element from this bag.
int	size() Determine the number of elements in this bag.
void	trimToSize() Reduce the current capacity of this bag to its actual size (i.e., the number of elements it contains).
static <E> ArrayBag<E>	union(ArrayBag<E> b1, ArrayBag<E> b2) Create a new bag that contains all the elements from two other bags.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ArrayBag

public ArrayBag()

Initialize an empty bag with an initial capacity of 10. Note that the addItem method works efficiently (without needing more memory) until this capacity is reached.

Parameters:

- - none

Postcondition:

This bag is empty and has an initial capacity of 10.

Throws:

java.lang.OutOfMemoryError - Indicates insufficient memory for: new Object[10].

ArrayBag

public ArrayBag(int initialCapacity)

Initialize an empty bag with a specified initial capacity. Note that the addItem method works efficiently (without needing more memory) until this capacity is reached.

Parameters:

initialCapacity - the initial capacity of this bag

Precondition:

initialCapacity is non-negative.

Postcondition:

This bag is empty and has the given initial capacity.

Throws:

java.lang.IllegalArgumentException - Indicates that initialCapacity is negative.

java.lang.OutOfMemoryError - Indicates insufficient memory for: new Object[initialCapacity].

Method Detail

add

public void add(E element)

Add a new element to this bag. If the new element would take this bag beyond its current capacity, then the capacity is increased before adding the new element.

Parameters:

element - the new element that is being inserted

Postcondition:

A new copy of the element has been added to this bag.

Throws:

java.lang.OutOfMemoryError - Indicates insufficient memory for increasing the bag's capacity.

Note:

An attempt to increase the capacity beyond Integer.MAX_VALUE will cause the bag to fail with an arithmetic overflow.

addMany

public void addMany(E... elements)

Add new elements to this bag. If the new elements would take this bag beyond its current capacity, then the capacity is increased before adding the new elements.

Parameters:

elements - (a variable-arity argument) one or more new elements that are being inserted

Postcondition:

A new copy of the element has been added to this bag.

Throws:

java.lang.OutOfMemoryError - Indicates insufficient memory for increasing the bag's capacity.

Note:

An attempt to increase the capacity beyond Integer.MAX_VALUE will cause the bag to fail with an arithmetic overflow.

addAll

public void addAll(ArrayBag<E> addend)

Add the contents of another bag to this bag.

Parameters:

addend - a bag whose contents will be added to this bag

Precondition:

The parameter, addend, is not null.

Postcondition:

The elements from addend have been added to this bag.

Throws:

java.lang.NullPointerException - Indicates that addend is null.

java.lang.OutOfMemoryError - Indicates insufficient memory to increase the size of the bag.

Note:

An attempt to increase the capacity beyond Integer.MAX_VALUE will cause an arithmetic overflow that will cause the bag to fail. Such large collections should use a different bag implementation.

clone

public ArrayBag<E> clone()

Generate a copy of this bag.

Overrides:

clone in class java.lang.Object

Parameters:

- - none

Returns:

The return value is a copy of this bag. Subsequent changes to the copy will not affect the original, nor vice versa.

Throws:

java.lang.OutOfMemoryError - Indicates insufficient memory for creating the clone.

countOccurrences

public int countOccurrences(E target)

Accessor method to count the number of occurrences of a particular element in this bag.

Parameters:

target - the element that needs to be counted

Returns:

the number of times that target occurs in this bag

ensureCapacity

public void ensureCapacity(int minimumCapacity)

Change the current capacity of this bag.

Parameters:

minimumCapacity - the new capacity for this bag

Postcondition:

This bag's capacity has been changed to at least minimumCapacity. If the capacity was already at or greater than minimumCapacity, then the capacity is left unchanged.

Throws:

java.lang.OutOfMemoryError - Indicates insufficient memory for: new Object[minimumCapacity].

getCapacity

public int getCapacity()

Accessor method to get the current capacity of this bag. The add method works efficiently (without needing more memory) until this capacity is reached.

Parameters:

- - none

Returns:

the current capacity of this bag

grab

public E grab()

Accessor method to retrieve a random element from this bag.

Parameters:

- - none

Precondition:

This bag is not empty.

Returns:

a randomly selected element from this bag

Throws:

java.lang.IllegalStateException - Indicates that the bag is empty.

remove

public boolean remove(E target)

Remove one copy of a specified element from this bag.

Parameters:

target - the element to remove from the bag

Postcondition:

If target was found in the bag, then one copy of target has been removed and the method returns true. Otherwise the bag remains unchanged and the method returns false.

size

public int size()

Determine the number of elements in this bag.

Parameters:

- - none

Returns:

the number of elements in this bag

trimToSize

public void trimToSize()

Reduce the current capacity of this bag to its actual size (i.e., the number of elements it contains).

Parameters:

- - none

Postcondition:

This bag's capacity has been changed to its current size.

Throws:

java.lang.OutOfMemoryError - Indicates insufficient memory for altering the capacity.

union

public static <E> ArrayBag<E> union(ArrayBag<E> b1,
                                    ArrayBag<E> b2)

Create a new bag that contains all the elements from two other bags.

Parameters:

b1 - the first of two bags

b2 - the second of two bags

Precondition:

Neither b1 nor b2 is null, and b1.getCapacity( ) + b2.getCapacity( ) <= Integer.MAX_VALUE.

Returns:

the union of b1 and b2

Throws:

NullPointerException. - Indicates that one of the arguments is null.

java.lang.OutOfMemoryError - Indicates insufficient memory for the new bag.

Note:

An attempt to create a bag with a capacity beyond Integer.MAX_VALUE will cause an arithmetic overflow that will cause the bag to fail. Such large collections should use a different bag implementation.