com.neeve.lang
Class XCollection<E>

java.lang.Object
  com.neeve.lang.XCollection<E>

All Implemented Interfaces:

Iterable<E>, Collection<E>

Direct Known Subclasses:

XIndexedList, XLinkedList

public abstract class XCollection<E>
extends Object
implements Collection<E>

This class represents collections which can quickly be iterated over (forward or backward) and which an be made thread-safe and/or unmodifiable.

XCollections can be iterated over without creating new objects and without using iterators . [code] public boolean search(Object item, XCollection c) { for (Record r = c.head(), end = c.tail(); (r = r.getNext()) != end;) { if (item.equals(c.valueOf(r))) return true; } return false; } [/code]

Alternatively XCollection}s can be iterated over using reusableIterator(), Utilization of this iterators does not introduce garbage because it is created once. This iterator may not be used concurrently by multiple threads as they are single instance by nature.

XCollections are thread-safe when marked shared (can be read, iterated over or modified concurrently). [code] public class Foo { private static final Collection INSTANCES = new XLinkedHashMap().shared(); public Foo() { INSTANCES.add(this); } public static void showInstances() { for (Foo foo : INSTANCES) { // Iterations are thread-safe even if new Foo instances are added. System.out.println(foo); } } }[/code]

This class was based on collections code from http://javolution.org, but modified for use outside of realtime jvms.

Nested Class Summary

static interface

XCollection.Record This interface represents the collection records which can directly be iterated over.

Method Summary

boolean	add(E value) Appends the specified value to the end of this collection (optional operation).
boolean	addAll(Collection<? extends E> c) Appends all of the values in the specified collection to the end of this collection, in the order that they are returned by the specified collection's iterator.
void	clear() Removes all of the values from this collection (optional operation).
boolean	contains(Object value) Indicates if this collection contains the specified value.
boolean	containsAll(Collection<?> c) Indicates if this collection contains all of the values of the specified collection.
void	copyTo(Collection<? super E> c) Copies the elements from this collection into another collection.
abstract void	delete(XCollection.Record record) Deletes the specified record from this collection.
boolean	equals(Object obj) Compares the specified object with this collection for equality.
int	hashCode() Returns the hash code for this collection.
abstract XCollection.Record	head() Returns the head record of this collection; it is the record such as head().getNext() holds the first collection value.
boolean	isEmpty() Indicates if this collection is empty.
XIterator<E>	iterator() Returns an iterator over the elements in this collection
boolean	remove(Object value) Removes the first occurrence in this collection of the specified value (optional operation).
boolean	removeAll(Collection<?> c) Removes from this collection all the values that are contained in the specified collection.
boolean	retainAll(Collection<?> c) Retains only the values in this collection that are contained in the specified collection.
XIterator<E>	reusableIterator() Returns an iterator over the elements in this collection.
Collection<E>	shared() Returns a thread-safe read-write view of this collection.
abstract int	size() Returns the number of values in this collection.
abstract XCollection.Record	tail() Returns the tail record of this collection; it is the record such as tail().getPrevious() holds the last collection value.
Object[]	toArray() Returns a new array allocated on the heap containing all of the values in this collection in proper sequence.
<T> T[]	toArray(T[] array) Fills the specified array with the values of this collection in the proper sequence.
String	toString() Returns a string representation of this collection.
Collection<E>	unmodifiable() Returns the unmodifiable view associated to this collection.
abstract E	valueOf(XCollection.Record record) Returns the collection value for the specified record.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Method Detail

size

public abstract int size()

Returns the number of values in this collection.

Specified by:

size in interface Collection<E>

Returns:

the number of values.

head

public abstract XCollection.Record head()

Returns the head record of this collection; it is the record such as head().getNext() holds the first collection value.

Returns:

the head record.

tail

public abstract XCollection.Record tail()

Returns the tail record of this collection; it is the record such as tail().getPrevious() holds the last collection value.

Returns:

the tail record.

valueOf

public abstract E valueOf(XCollection.Record record)

Returns the collection value for the specified record.

Parameters:

record - the record whose current value is returned.

Returns:

the current value.

delete

public abstract void delete(XCollection.Record record)

Deletes the specified record from this collection.

Implementation must ensure that removing a record from the collection does not affect in any way the records preceding the record being removed (it might affect the next records though, e.g. in a list collection, the indices of the subsequent records will change).

Parameters:

record - the record to be removed.

Throws:

UnsupportedOperationException - if not supported.

unmodifiable

public Collection<E> unmodifiable()

Returns the unmodifiable view associated to this collection. Attempts to modify the returned collection result in an UnsupportedOperationException being thrown.

Returns:

the unmodifiable view over this collection.

shared

public Collection<E> shared()

Returns a thread-safe read-write view of this collection.

The default implementation performs synchronization on read and write. Sub-classes may provide more efficient implementation (e.g. only synchronizing on writes modifying the internal data structure).

Having a shared collection does not mean that modifications made by onethread are automatically viewed by others thread. Which in practice is not an issue. In a well-behaved system, threads need to synchronize only at predetermined synchronization points (the fewer the better).

Returns:

a thread-safe collection.

iterator

public XIterator<E> iterator()

Returns an iterator over the elements in this collection

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface Collection<E>

Returns:

an iterator over this collection's elements.

reusableIterator

public XIterator<E> reusableIterator()

Returns an iterator over the elements in this collection. This iterator may only be used by a single thread at a time. This method invokes XIterator.toFirst() on the iterator prior to returning it.

Returns:

an iterator over this collection's elements.

add

public boolean add(E value)

Appends the specified value to the end of this collection (optional operation).

Note: This default implementation always throws UnsupportedOperationException.

Specified by:

add in interface Collection<E>

Parameters:

value - the value to be appended to this collection.

Returns:

true (as per the general contract of the Collection.add method).

Throws:

UnsupportedOperationException - if not supported.

remove

public boolean remove(Object value)

Removes the first occurrence in this collection of the specified value (optional operation).

Specified by:

remove in interface Collection<E>

Parameters:

value - the value to be removed from this collection.

Returns:

true if this collection contained the specified value; false otherwise.

Throws:

UnsupportedOperationException - if not supported.

clear

public void clear()

Removes all of the values from this collection (optional operation).

Specified by:

clear in interface Collection<E>

Throws:

UnsupportedOperationException - if not supported.

isEmpty

public final boolean isEmpty()

Indicates if this collection is empty.

Specified by:

isEmpty in interface Collection<E>

Returns:

true if this collection contains no value; false otherwise.

contains

public boolean contains(Object value)

Indicates if this collection contains the specified value.

Specified by:

contains in interface Collection<E>

Parameters:

value - the value whose presence in this collection is to be tested.

Returns:

true if this collection contains the specified value;false otherwise.

addAll

public boolean addAll(Collection<? extends E> c)

Appends all of the values in the specified collection to the end of this collection, in the order that they are returned by the specified collection's iterator.

Specified by:

addAll in interface Collection<E>

Parameters:

c - collection whose values are to be added to this collection.

Returns:

true if this collection changed as a result of the call; false otherwise.

containsAll

public boolean containsAll(Collection<?> c)

Indicates if this collection contains all of the values of the specified collection.

Specified by:

containsAll in interface Collection<E>

Parameters:

c - collection to be checked for containment in this collection.

Returns:

true if this collection contains all of the values of the specified collection; false otherwise.

removeAll

public boolean removeAll(Collection<?> c)

Removes from this collection all the values that are contained in the specified collection.

Specified by:

removeAll in interface Collection<E>

Parameters:

c - collection that defines which values will be removed from this collection.

Returns:

true if this collection changed as a result of the call; false otherwise.

retainAll

public boolean retainAll(Collection<?> c)

Retains only the values in this collection that are contained in the specified collection.

Specified by:

retainAll in interface Collection<E>

Parameters:

c - collection that defines which values this set will retain.

Returns:

true if this collection changed as a result of the call; false otherwise.

copyTo

public void copyTo(Collection<? super E> c)

Copies the elements from this collection into another collection.

Parameters:

c - The collection into which this should be copied.

toArray

public Object[] toArray()

Returns a new array allocated on the heap containing all of the values in this collection in proper sequence.

Note: To avoid heap allocation toArray(Object[]) is recommended.

Specified by:

toArray in interface Collection<E>

Returns:

toArray(new Object[size()])

toArray

public <T> T[] toArray(T[] array)

Fills the specified array with the values of this collection in the proper sequence.

Specified by:

toArray in interface Collection<E>

Parameters:

array - the array into which the values of this collection are to be stored.

Returns:

the specified array.

toString

public String toString()

Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters ", " (comma and space). Elements are converted to strings as by String.valueOf(Object).

Overrides:

toString in class Object

Returns:

a string representation of this collection

equals

public boolean equals(Object obj)

Compares the specified object with this collection for equality. The default behavior is to consider two collections equal if they hold the same values and have the same iterative order if any of the collections is an ordered collection (List instances).

Specified by:

equals in interface Collection<E>

Overrides:

equals in class Object

Parameters:

obj - the object to be compared for equality with this collection

Returns:

true if the specified object is a collection with the same content and iteration order when necessary; false otherwise.

hashCode

public int hashCode()

Returns the hash code for this collection. For non-ordered collection the hashcode of this collection is the sum of the hashcode of its values.

Specified by:

hashCode in interface Collection<E>

Overrides:

hashCode in class Object

Returns:

the hash code for this collection.