Class FastArrayList<E>
- All Implemented Interfaces:
Serializable
,Cloneable
,Iterable<E>
,Collection<E>
,List<E>
,RandomAccess
The size, isEmpty, get, set, iterator, and listIterator operations run in constant time. The add operation runs in amortized constant time, that is, adding n elements requires O(n) time. All of the other operations run in linear time (roughly speaking). The constant factor is low compared to that for the LinkedList implementation.
Each ArrayList instance has a capacity. The capacity is the size of the array used to store the elements in the list. It is always at least as large as the list size. As elements are added to an ArrayList, its capacity grows automatically. The details of the growth policy are not specified beyond the fact that adding an element has constant amortized time cost.
An application can increase the capacity of an ArrayList instance before adding a large number of elements using the ensureCapacity operation. This may reduce the amount of incremental reallocation.
Note that this implementation is not synchronized. If
multiple threads access an ArrayList instance concurrently, and at
least one of the threads modifies the list structurally, it must be
synchronized externally. (A structural modification is any operation that
adds or deletes one or more elements, or explicitly resizes the backing
array; merely setting the value of an element is not a structural
modification.) This is typically accomplished by synchronizing on some object
that naturally encapsulates the list.
If no such object exists, the list should be "wrapped" using the
Collections.synchronizedList
method.
This is best done at creation time, to prevent accidental unsynchronized
access to the list:
List list = Collections.synchronizedList(new ArrayList(...));
The iterators returned by this class's
iterator
and listIterator
methods are fail-fast: if the list is structurally modified at any
time after the iterator is created, in any way except through the iterator's
own remove
or add
methods, the iterator will throw a
ConcurrentModificationException
. Thus, in the face of concurrent
modification, the iterator fails quickly and cleanly, rather than risking
arbitrary, non-deterministic behavior at an undetermined time in the future.
Note that the fail-fast behavior of an iterator cannot be guaranteed as it
is, generally speaking, impossible to make any hard guarantees in the
presence of unsynchronized concurrent modification. Fail-fast iterators throw
ConcurrentModificationException
on a best-effort basis. Therefore, it
would be wrong to write a program that depended on this exception for its
correctness: the fail-fast behavior of iterators should be used only to
detect bugs.
This class is a member of the Java Collections Framework.
- Since:
- 1.2
- See Also:
-
Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprivate class
An optimized version of AbstractList.Itrprivate class
An optimized version of AbstractList.ListItrprivate class
-
Field Summary
FieldsModifier and TypeFieldDescriptionprivate static final int
Default initial capacity.private Object[]
The array buffer into which the elements of the ArrayList are stored.private static final Object[]
Shared empty array instance used for empty instances.private int
private boolean
private static final int
The maximum size of array to allocate.private static final long
private int
The size of the ArrayList (the number of elements it contains).Fields inherited from class java.util.AbstractList
modCount
-
Constructor Summary
ConstructorsConstructorDescriptionConstructs an empty list with an initial capacity of ten.FastArrayList
(int initialCapacity) Constructs an empty list with the specified initial capacity.FastArrayList
(E... c) FastArrayList
(Collection<? extends E> c) Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.FastArrayList
(Enumeration<E> enumeration) -
Method Summary
Modifier and TypeMethodDescriptionvoid
Inserts the specified element at the specified position in this list.boolean
Appends the specified element to the end of this list.boolean
addAll
(int index, Collection<? extends E> c) Inserts all of the elements in the specified collection into this list, starting at the specified position.boolean
addAll
(Collection<? extends E> c) Appends 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.private boolean
batchRemove
(Collection<?> c, boolean complement) void
clear()
Removes all of the elements from this list.clone()
Returns a shallow copy of this ArrayList instance.boolean
Returns true if this list contains the specified element.(package private) E
elementData
(int index) void
ensureCapacity
(int minCapacity) Increases 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.private void
ensureCapacityInternal
(int minCapacity) private void
ensureExplicitCapacity
(int minCapacity) private void
fastRemove
(int index) get
(int index) Returns the element at the specified position in this list.private void
grow
(int minCapacity) Increases the capacity to ensure that it can hold at least the number of elements specified by the minimum capacity argument.int
hashCode()
private static int
hugeCapacity
(int minCapacity) int
Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.boolean
isEmpty()
Returns true if this list contains no elements.iterator()
Returns an iterator over the elements in this list in proper sequence.int
Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.Returns a list iterator over the elements in this list (in proper sequence).listIterator
(int index) Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list.private void
Reconstitute the ArrayList instance from a stream (that is, deserialize it).remove
(int index) Removes the element at the specified position in this list.boolean
Removes the first occurrence of the specified element from this list, if it is present.boolean
removeAll
(Collection<?> c) Removes from this list all of its elements that are contained in the specified collection.protected void
removeRange
(int fromIndex, int toIndex) Removes from this list all of the elements whose index is betweenfromIndex
, inclusive, andtoIndex
, exclusive.boolean
retainAll
(Collection<?> c) Retains only the elements in this list that are contained in the specified collection.Replaces the element at the specified position in this list with the specified element.int
size()
Returns the number of elements in this list.subList
(int fromIndex, int toIndex) Returns a view of the portion of this list between the specifiedfromIndex
, inclusive, andtoIndex
, exclusive.(package private) static void
subListRangeCheck
(int fromIndex, int toIndex, int size) Object[]
toArray()
Returns an array containing all of the elements in this list in proper sequence (from first to last element).<T> T[]
toArray
(T[] a) Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array.void
Trims the capacity of this ArrayList instance to be the list's current size.private void
Save the state of the ArrayList instance to a stream (that is, serialize it).Methods inherited from class java.util.AbstractList
equals
Methods inherited from class java.util.AbstractCollection
containsAll, toString
Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
Methods inherited from interface java.util.Collection
parallelStream, removeIf, stream, toArray
Methods inherited from interface java.util.List
containsAll, equals, replaceAll, sort, spliterator
-
Field Details
-
serialVersionUID
private static final long serialVersionUID- See Also:
-
DEFAULT_CAPACITY
private static final int DEFAULT_CAPACITYDefault initial capacity.- See Also:
-
EMPTY_ELEMENTDATA
Shared empty array instance used for empty instances. -
hashCodeUpToDate
private boolean hashCodeUpToDate -
hashCode
private int hashCode -
elementData
The array buffer into which the elements of the ArrayList are stored. The capacity of the ArrayList is the length of this array buffer. Any empty ArrayList with elementData == EMPTY_ELEMENTDATA will be expanded to DEFAULT_CAPACITY when the first element is added. -
size
private int sizeThe size of the ArrayList (the number of elements it contains). -
MAX_ARRAY_SIZE
private static final int MAX_ARRAY_SIZEThe maximum size of array to allocate. Some VMs reserve some header words in an array. Attempts to allocate larger arrays may result in OutOfMemoryError: Requested array size exceeds VM limit- See Also:
-
-
Constructor Details
-
FastArrayList
public FastArrayList(int initialCapacity) Constructs an empty list with the specified initial capacity.- Parameters:
initialCapacity
- the initial capacity of the list- Throws:
IllegalArgumentException
- if the specified initial capacity is negative
-
FastArrayList
public FastArrayList()Constructs an empty list with an initial capacity of ten. -
FastArrayList
Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.- Parameters:
c
- the collection whose elements are to be placed into this list- Throws:
NullPointerException
- if the specified collection is null
-
FastArrayList
-
FastArrayList
-
-
Method Details
-
hashCode
public int hashCode()- Specified by:
hashCode
in interfaceCollection<E>
- Specified by:
hashCode
in interfaceList<E>
- Overrides:
hashCode
in classAbstractList<E>
-
trimToSize
public void trimToSize()Trims the capacity of this ArrayList instance to be the list's current size. An application can use this operation to minimize the storage of an ArrayList instance. -
ensureCapacity
public void ensureCapacity(int minCapacity) Increases 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.- Parameters:
minCapacity
- the desired minimum capacity
-
ensureCapacityInternal
private void ensureCapacityInternal(int minCapacity) -
ensureExplicitCapacity
private void ensureExplicitCapacity(int minCapacity) -
grow
private void grow(int minCapacity) Increases the capacity to ensure that it can hold at least the number of elements specified by the minimum capacity argument.- Parameters:
minCapacity
- the desired minimum capacity
-
hugeCapacity
private static int hugeCapacity(int minCapacity) -
size
public int size()Returns the number of elements in this list.- Specified by:
size
in interfaceCollection<E>
- Specified by:
size
in interfaceList<E>
- Specified by:
size
in classAbstractCollection<E>
- Returns:
- the number of elements in this list
-
isEmpty
public boolean isEmpty()Returns true if this list contains no elements.- Specified by:
isEmpty
in interfaceCollection<E>
- Specified by:
isEmpty
in interfaceList<E>
- Overrides:
isEmpty
in classAbstractCollection<E>
- Returns:
- true if this list contains no elements
-
contains
Returns true if this list contains the specified element. More formally, returns true if and only if this list contains at least one element e such that (o==null ? e==null : o.equals(e)).- Specified by:
contains
in interfaceCollection<E>
- Specified by:
contains
in interfaceList<E>
- Overrides:
contains
in classAbstractCollection<E>
- Parameters:
o
- element whose presence in this list is to be tested- Returns:
- true if this list contains the specified element
-
indexOf
Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index. -
lastIndexOf
Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the highest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.- Specified by:
lastIndexOf
in interfaceList<E>
- Overrides:
lastIndexOf
in classAbstractList<E>
-
clone
Returns a shallow copy of this ArrayList instance. (The elements themselves are not copied.) -
toArray
Returns an array containing all of the elements in this list in proper sequence (from first to last element).The returned array will be "safe" in that no references to it are maintained by this list. (In other words, this method must allocate a new array). The caller is thus free to modify the returned array.
This method acts as bridge between array-based and collection-based APIs.
- Specified by:
toArray
in interfaceCollection<E>
- Specified by:
toArray
in interfaceList<E>
- Overrides:
toArray
in classAbstractCollection<E>
- Returns:
- an array containing all of the elements in this list in proper sequence
-
toArray
public <T> T[] toArray(T[] a) Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array. If the list fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this list.If the list fits in the specified array with room to spare (i.e., the array has more elements than the list), the element in the array immediately following the end of the collection is set to null. (This is useful in determining the length of the list only if the caller knows that the list does not contain any null elements.)
- Specified by:
toArray
in interfaceCollection<E>
- Specified by:
toArray
in interfaceList<E>
- Overrides:
toArray
in classAbstractCollection<E>
- Parameters:
a
- the array into which the elements of the list are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.- Returns:
- an array containing the elements of the list
- Throws:
ArrayStoreException
- if the runtime type of the specified array is not a supertype of the runtime type of every element in this listNullPointerException
- if the specified array is null
-
elementData
-
get
Returns the element at the specified position in this list.- Specified by:
get
in interfaceList<E>
- Specified by:
get
in classAbstractList<E>
- Parameters:
index
- index of the element to return- Returns:
- the element at the specified position in this list
- Throws:
IndexOutOfBoundsException
-
set
Replaces the element at the specified position in this list with the specified element.- Specified by:
set
in interfaceList<E>
- Specified by:
set
in classAbstractList<E>
- Parameters:
index
- index of the element to replaceelement
- element to be stored at the specified position- Returns:
- the element previously at the specified position
- Throws:
IndexOutOfBoundsException
-
add
Appends the specified element to the end of this list.- Specified by:
add
in interfaceCollection<E>
- Specified by:
add
in interfaceList<E>
- Specified by:
add
in classAbstractList<E>
- Parameters:
e
- element to be appended to this list- Returns:
- true (as specified by
Collection.add(E)
)
-
add
Inserts the specified element at the specified position in this list. Shifts the element currently at that position (if any) and any subsequent elements to the right (adds one to their indices).- Specified by:
add
in interfaceList<E>
- Specified by:
add
in classAbstractList<E>
- Parameters:
index
- index at which the specified element is to be insertedelement
- element to be inserted- Throws:
IndexOutOfBoundsException
-
remove
Removes the element at the specified position in this list. Shifts any subsequent elements to the left (subtracts one from their indices).- Specified by:
remove
in interfaceList<E>
- Specified by:
remove
in classAbstractList<E>
- Parameters:
index
- the index of the element to be removed- Returns:
- the element that was removed from the list
- Throws:
IndexOutOfBoundsException
-
remove
Removes the first occurrence of the specified element from this list, if it is present. If the list does not contain the element, it is unchanged. More formally, removes the element with the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))) (if such an element exists). Returns true if this list contained the specified element (or equivalently, if this list changed as a result of the call).- Specified by:
remove
in interfaceCollection<E>
- Specified by:
remove
in interfaceList<E>
- Overrides:
remove
in classAbstractCollection<E>
- Parameters:
o
- element to be removed from this list, if present- Returns:
- true if this list contained the specified element
-
fastRemove
private void fastRemove(int index) -
clear
public void clear()Removes all of the elements from this list. The list will be empty after this call returns.- Specified by:
clear
in interfaceCollection<E>
- Specified by:
clear
in interfaceList<E>
- Specified by:
clear
in classAbstractList<E>
-
addAll
Appends 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. The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. (This implies that the behavior of this call is undefined if the specified collection is this list, and this list is nonempty.)- Specified by:
addAll
in interfaceCollection<E>
- Specified by:
addAll
in interfaceList<E>
- Overrides:
addAll
in classAbstractCollection<E>
- Parameters:
c
- collection containing elements to be added to this list- Returns:
- true if this list changed as a result of the call
- Throws:
NullPointerException
- if the specified collection is null
-
addAll
Inserts all of the elements in the specified collection into this list, starting at the specified position. Shifts the element currently at that position (if any) and any subsequent elements to the right (increases their indices). The new elements will appear in the list in the order that they are returned by the specified collection's iterator.- Specified by:
addAll
in interfaceList<E>
- Overrides:
addAll
in classAbstractList<E>
- Parameters:
index
- index at which to insert the first element from the specified collectionc
- collection containing elements to be added to this list- Returns:
- true if this list changed as a result of the call
- Throws:
IndexOutOfBoundsException
NullPointerException
- if the specified collection is null
-
removeRange
protected void removeRange(int fromIndex, int toIndex) Removes from this list all of the elements whose index is betweenfromIndex
, inclusive, andtoIndex
, exclusive. Shifts any succeeding elements to the left (reduces their index). This call shortens the list by(toIndex - fromIndex)
elements. (IftoIndex==fromIndex
, this operation has no effect.)- Overrides:
removeRange
in classAbstractList<E>
- Throws:
IndexOutOfBoundsException
- iffromIndex
ortoIndex
is out of range (fromIndex < 0 || fromIndex >= size() || toIndex > size() || toIndex < fromIndex
)
-
removeAll
Removes from this list all of its elements that are contained in the specified collection.- Specified by:
removeAll
in interfaceCollection<E>
- Specified by:
removeAll
in interfaceList<E>
- Overrides:
removeAll
in classAbstractCollection<E>
- Parameters:
c
- collection containing elements to be removed from this list- Returns:
true
if this list changed as a result of the call- Throws:
ClassCastException
- if the class of an element of this list is incompatible with the specified collection (optional)NullPointerException
- if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null- See Also:
-
retainAll
Retains only the elements in this list that are contained in the specified collection. In other words, removes from this list all of its elements that are not contained in the specified collection.- Specified by:
retainAll
in interfaceCollection<E>
- Specified by:
retainAll
in interfaceList<E>
- Overrides:
retainAll
in classAbstractCollection<E>
- Parameters:
c
- collection containing elements to be retained in this list- Returns:
true
if this list changed as a result of the call- Throws:
ClassCastException
- if the class of an element of this list is incompatible with the specified collection (optional)NullPointerException
- if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null- See Also:
-
batchRemove
-
writeObject
Save the state of the ArrayList instance to a stream (that is, serialize it).- Throws:
IOException
-
readObject
Reconstitute the ArrayList instance from a stream (that is, deserialize it).- Throws:
IOException
ClassNotFoundException
-
listIterator
Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list. The specified index indicates the first element that would be returned by an initial call tonext
. An initial call toprevious
would return the element with the specified index minus one.The returned list iterator is fail-fast.
- Specified by:
listIterator
in interfaceList<E>
- Overrides:
listIterator
in classAbstractList<E>
- Throws:
IndexOutOfBoundsException
-
listIterator
Returns a list iterator over the elements in this list (in proper sequence).The returned list iterator is fail-fast.
- Specified by:
listIterator
in interfaceList<E>
- Overrides:
listIterator
in classAbstractList<E>
- See Also:
-
iterator
Returns an iterator over the elements in this list in proper sequence.The returned iterator is fail-fast.
-
subList
Returns a view of the portion of this list between the specifiedfromIndex
, inclusive, andtoIndex
, exclusive. (IffromIndex
andtoIndex
are equal, the returned list is empty.) The returned list is backed by this list, so non-structural changes in the returned list are reflected in this list, and vice-versa. The returned list supports all of the optional list operations.This method eliminates the need for explicit range operations (of the sort that commonly exist for arrays). Any operation that expects a list can be used as a range operation by passing a subList view instead of a whole list. For example, the following idiom removes a range of elements from a list:
list.subList(from, to).clear();
Similar idioms may be constructed forindexOf(Object)
andlastIndexOf(Object)
, and all of the algorithms in theCollections
class can be applied to a subList.The semantics of the list returned by this method become undefined if the backing list (i.e., this list) is structurally modified in any way other than via the returned list. (Structural modifications are those that change the size of this list, or otherwise perturb it in such a fashion that iterations in progress may yield incorrect results.)
- Specified by:
subList
in interfaceList<E>
- Overrides:
subList
in classAbstractList<E>
- Throws:
IndexOutOfBoundsException
IllegalArgumentException
-
subListRangeCheck
static void subListRangeCheck(int fromIndex, int toIndex, int size)
-