org.apache.commons.collections
public class FastArrayList extends ArrayList
A customized implementation of java.util.ArrayList
designed
to operate in a multithreaded environment where the large majority of
method calls are read-only, instead of structural changes. When operating
in "fast" mode, read calls are non-synchronized and write calls perform the
following steps:
When first created, objects of this class default to "slow" mode, where
all accesses of any type are synchronized but no cloning takes place. This
is appropriate for initially populating the collection, followed by a switch
to "fast" mode (by calling setFast(true)
) after initialization
is complete.
NOTE: If you are creating and accessing an
ArrayList
only within a single thread, you should use
java.util.ArrayList
directly (with no synchronization), for
maximum performance.
NOTE: This class is not cross-platform. Using it may cause unexpected failures on some architectures. It suffers from the same problems as the double-checked locking idiom. In particular, the instruction that clones the internal collection and the instruction that sets the internal reference to the clone can be executed or perceived out-of-order. This means that any read operation might fail unexpectedly, as it may be reading the state of the internal collection before the internal collection is fully formed. For more information on the double-checked locking idiom, see the Double-Checked Locking Idiom Is Broken Declaration.
Since: Commons Collections 1.0
Version: $Revision: 178303 $ $Date: 2005-05-24 23:39:51 +0100 (Tue, 24 May 2005) $
Field Summary | |
---|---|
protected boolean | fast
Are we operating in "fast" mode? |
protected ArrayList | list
The underlying list we are managing. |
Constructor Summary | |
---|---|
FastArrayList()
Construct a an empty list. | |
FastArrayList(int capacity)
Construct an empty list with the specified capacity.
| |
FastArrayList(Collection collection)
Construct a list containing the elements of the specified collection,
in the order they are returned by the collection's iterator.
|
Method Summary | |
---|---|
boolean | add(Object element)
Appends the specified element to the end of this list.
|
void | add(int index, Object element)
Insert the specified element at the specified position in this list,
and shift all remaining elements up one position.
|
boolean | addAll(Collection collection)
Append all of the elements in the specified Collection to the end
of this list, in the order that they are returned by the specified
Collection's Iterator.
|
boolean | addAll(int index, Collection collection)
Insert all of the elements in the specified Collection at the specified
position in this list, and shift any previous elements upwards as
needed.
|
void | clear()
Remove all of the elements from this list. |
Object | clone()
Return a shallow copy of this FastArrayList instance.
|
boolean | contains(Object element)
Return true if this list contains the specified element.
|
boolean | containsAll(Collection collection)
Return true if this list contains all of the elements
in the specified Collection.
|
void | ensureCapacity(int capacity)
Increase the capacity of this ArrayList instance, if
necessary, to ensure that it can hold at least the number of elements
specified by the minimum capacity argument.
|
boolean | equals(Object o)
Compare the specified object with this list for equality. |
Object | get(int index)
Return the element at the specified position in the list.
|
boolean | getFast()
Returns true if this list is operating in fast mode.
|
int | hashCode()
Return the hash code value for this list. |
int | indexOf(Object element)
Search for the first occurrence of the given argument, testing
for equality using the equals() method, and return
the corresponding index, or -1 if the object is not found.
|
boolean | isEmpty()
Test if this list has no elements. |
Iterator | iterator()
Return an iterator over the elements in this list in proper sequence.
|
int | lastIndexOf(Object element)
Search for the last occurrence of the given argument, testing
for equality using the equals() method, and return
the corresponding index, or -1 if the object is not found.
|
ListIterator | listIterator()
Return an iterator of the elements of this list, in proper sequence.
|
ListIterator | listIterator(int index)
Return an iterator of the elements of this list, in proper sequence,
starting at the specified position.
|
Object | remove(int index)
Remove the element at the specified position in the list, and shift
any subsequent elements down one position.
|
boolean | remove(Object element)
Remove the first occurrence of the specified element from the list,
and shift any subsequent elements down one position.
|
boolean | removeAll(Collection collection)
Remove from this collection all of its elements that are contained
in the specified collection.
|
boolean | retainAll(Collection collection)
Remove from this collection all of its elements except those that are
contained in the specified collection.
|
Object | set(int index, Object element)
Replace the element at the specified position in this list with
the specified element. |
void | setFast(boolean fast)
Sets whether this list will operate in fast mode.
|
int | size()
Return the number of elements in this list. |
List | subList(int fromIndex, int toIndex)
Return a view of the portion of this list between fromIndex
(inclusive) and toIndex (exclusive). |
Object[] | toArray()
Return an array containing all of the elements in this list in the
correct order. |
Object[] | toArray(Object[] array)
Return an array containing all of the elements in this list in the
correct order. |
String | toString()
Return a String representation of this object. |
void | trimToSize()
Trim the capacity of this ArrayList instance to be the
list's current size. |
Parameters: capacity The initial capacity of the empty list
Parameters: collection The collection whose elements initialize the contents of this list
Parameters: element The element to be appended
Parameters: index Index at which to insert this element element The element to be inserted
Throws: IndexOutOfBoundsException if the index is out of range
Parameters: collection The collection to be appended
Parameters: index Index at which insertion takes place collection The collection to be added
Throws: IndexOutOfBoundsException if the index is out of range
Throws: UnsupportedOperationException if clear()
is not supported by this list
FastArrayList
instance.
The elements themselves are not copied.true
if this list contains the specified element.
Parameters: element The element to test for
true
if this list contains all of the elements
in the specified Collection.
Parameters: collection Collection whose elements are to be checked
ArrayList
instance, if
necessary, to ensure that it can hold at least the number of elements
specified by the minimum capacity argument.
Parameters: capacity The new minimum capacity
List.equals
method.
Parameters: o Object to be compared to this list
Parameters: index The index of the element to return
Throws: IndexOutOfBoundsException if the index is out of range
Returns: true if this list is operating in fast mode
List.hashCode
method.equals()
method, and return
the corresponding index, or -1 if the object is not found.
Parameters: element The element to search for
Thread safety
The iterator returned is thread-safe ONLY in FAST mode.
In slow mode there is no way to synchronize, or make the iterator thread-safe.
In fast mode iteration and modification may occur in parallel on different threads, however there is a restriction. Modification must be EITHER via the Iterator interface methods OR the List interface. If a mixture of modification methods is used a ConcurrentModificationException is thrown from the iterator modification method. If the List modification methods are used the changes are NOT visible in the iterator (it shows the list contents at the time the iterator was created).
Returns: the iterator
equals()
method, and return
the corresponding index, or -1 if the object is not found.
Parameters: element The element to search for
Thread safety
The iterator returned is thread-safe ONLY in FAST mode.
In slow mode there is no way to synchronize, or make the iterator thread-safe.
In fast mode iteration and modification may occur in parallel on different threads, however there is a restriction. Modification must be EITHER via the Iterator interface methods OR the List interface. If a mixture of modification methods is used a ConcurrentModificationException is thrown from the iterator modification method. If the List modification methods are used the changes are NOT visible in the iterator (it shows the list contents at the time the iterator was created).
Returns: the list iterator
Thread safety
The iterator returned is thread-safe ONLY in FAST mode.
In slow mode there is no way to synchronize, or make the iterator thread-safe.
In fast mode iteration and modification may occur in parallel on different threads, however there is a restriction. Modification must be EITHER via the Iterator interface methods OR the List interface. If a mixture of modification methods is used a ConcurrentModificationException is thrown from the iterator modification method. If the List modification methods are used the changes are NOT visible in the iterator (it shows the list contents at the time the iterator was created).
Parameters: index The starting position of the iterator to return
Returns: the list iterator
Throws: IndexOutOfBoundsException if the index is out of range
Parameters: index Index of the element to be removed
Throws: IndexOutOfBoundsException if the index is out of range
Parameters: element Element to be removed
Parameters: collection Collection containing elements to be removed
Throws: UnsupportedOperationException if this optional operation is not supported by this list
Parameters: collection Collection containing elements to be retained
Throws: UnsupportedOperationException if this optional operation is not supported by this list
Parameters: index Index of the element to replace element The new element to be stored
Throws: IndexOutOfBoundsException if the index is out of range
Parameters: fast true if the list should operate in fast mode
Parameters: fromIndex The starting index of the sublist view toIndex The index after the end of the sublist view
Throws: IndexOutOfBoundsException if an index is out of range
Parameters: array Array defining the element type of the returned list
Throws: ArrayStoreException if the runtime type of array
is not a supertype of the runtime type of every element in this list
ArrayList
instance to be the
list's current size. An application can use this operation to minimize
the storage of an ArrayList
instance.