Top Description Fields Constructors Methods
ch.qos.logback.core.util

public Class COWArrayList<E>

extends Object
implements List<E>
Class Inheritance
All Implemented Interfaces
java.util.List, java.util.SequencedCollection, java.util.Collection, java.lang.Iterable
Imports
java.util.Collection, .Iterator, .List, .ListIterator, java.util.concurrent.CopyOnWriteArrayList, java.util.concurrent.atomic.AtomicBoolean
A GC-free lock-free thread-safe implementation of the List interface for use cases where iterations over the list vastly out-number modifications on the list.

Underneath, it wraps an instance of CopyOnWriteArrayList and exposes a copy of the array used by that instance.

Typical use: 

  COWArrayList<Integer> list = new COWArrayList(new Integer[0]);

  // modify the list
  list.add(1);
  list.add(2);

  Integer[] intArray = list.asTypedArray();
  int sum = 0;
  // iteration over the array is thread-safe
  for(int i = 0; i < intArray.length; i++) {
    sum != intArray[i];
  }

If the list is not modified, then repetitive calls to asTypedArray(), toArray() and toArray(Object[]) are guaranteed to be GC-free. Note that iterating over the list using COWArrayList#iterator() and COWArrayList#listIterator() are not GC-free.

Author
Ceki Gulcu
Since
1.1.10

Field Summary

Modifier and TypeField and Description
pack-priv AtomicBoolean
fresh

pack-priv final E[]
modelArray

pack-priv E[]
ourCopy

pack-priv CopyOnWriteArrayList<E>
underlyingList

Constructor Summary

AccessConstructor and Description
public
COWArrayList(E[] modelArray)

Method Summary

Modifier and TypeMethod and Description
public boolean
add(E
element to be appended to this list
e)

Implements java.util.List.add.

Appends the specified element to the end of this list (optional operation).
public void
add(int
index at which the specified element is to be inserted
index, E
element to be inserted
element)

Implements java.util.List.add.

Inserts the specified element at the specified position in this list (optional operation).
public boolean
addAll(Collection<? extends E>
collection containing elements to be added to this list
c)

Implements java.util.List.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 (optional operation).
public boolean
addAll(int
index at which to insert the first element from the specified collection
index, Collection<? extends E>
collection containing elements to be added to this list
col)

Implements java.util.List.addAll.

Inserts all of the elements in the specified collection into this list at the specified position (optional operation).
public void
addIfAbsent(E e)

public E[]
asTypedArray()

Return an array of type E[].

public void
clear()

Implements java.util.List.clear.

Removes all of the elements from this list (optional operation).
public boolean
contains(Object
element whose presence in this list is to be tested
o)

Implements java.util.List.contains.

Returns true if this list contains the specified element.
public boolean
containsAll(Collection<?>
collection to be checked for containment in this list
c)

Implements java.util.List.containsAll.

Returns true if this list contains all of the elements of the specified collection.
public E
get(int
index of the element to return
index)

Implements java.util.List.get.

Returns the element at the specified position in this list.
public int
indexOf(Object
element to search for
o)

Implements java.util.List.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.
public boolean
isEmpty()

Implements java.util.List.isEmpty.

Returns true if this list contains no elements.
private boolean
isFresh()

public Iterator<E>
iterator()

Implements java.util.List.iterator.

Returns an iterator over the elements in this list in proper sequence.
public int
lastIndexOf(Object
element to search for
o)

Implements java.util.List.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.
public ListIterator<E>
listIterator()

Implements java.util.List.listIterator.

Returns a list iterator over the elements in this list (in proper sequence).
public ListIterator<E>
listIterator(int
index of the first element to be returned from the list iterator (by a call to next)
index)

Implements java.util.List.listIterator.

Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list.
private void
markAsStale()

private void
refreshCopy()

private void
refreshCopyIfNecessary()

public boolean
remove(Object
element to be removed from this list, if present
o)

Implements java.util.List.remove.

Removes the first occurrence of the specified element from this list, if it is present (optional operation).
public E
remove(int
the index of the element to be removed
index)

Implements java.util.List.remove.

Removes the element at the specified position in this list (optional operation).
public boolean
removeAll(Collection<?>
collection containing elements to be removed from this list
col)

Implements java.util.List.removeAll.

Removes from this list all of its elements that are contained in the specified collection (optional operation).
public boolean
retainAll(Collection<?>
collection containing elements to be retained in this list
col)

Implements java.util.List.retainAll.

Retains only the elements in this list that are contained in the specified collection (optional operation).
public E
set(int
index of the element to replace
index, E
element to be stored at the specified position
element)

Implements java.util.List.set.

Replaces the element at the specified position in this list with the specified element (optional operation).
public int
size()

Implements java.util.List.size.

Returns the number of elements in this list.
public List<E>
subList(int
low endpoint (inclusive) of the subList
fromIndex, int
high endpoint (exclusive) of the subList
toIndex)

Implements java.util.List.subList.

Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive.
public Object[]
toArray()

Implements java.util.List.toArray.

Returns an array containing all of the elements in this list in proper sequence (from first to last element).
public <T> T[]
toArray(T[]
the array into which the elements of this list are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.
a)

Implements java.util.List.toArray.

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.
Inherited from java.lang.Object:
cloneequalsfinalizegetClasshashCodenotifynotifyAlltoStringwaitwaitwait

Field Detail

freshback to summary
pack-priv AtomicBoolean fresh
modelArrayback to summary
pack-priv final E[] modelArray
ourCopyback to summary
pack-priv E[] ourCopy
underlyingListback to summary
pack-priv CopyOnWriteArrayList<E> underlyingList

Constructor Detail

COWArrayListback to summary
public COWArrayList(E[] modelArray)

Method Detail

addback to summary
public boolean add(E e)

Implements java.util.List.add.

Doc from java.util.List.add.

Appends the specified element to the end of this list (optional operation).

Lists that support this operation may place limitations on what elements may be added to this list. In particular, some lists will refuse to add null elements, and others will impose restrictions on the type of elements that may be added. List classes should clearly specify in their documentation any restrictions on what elements may be added.

Parameters
e:E

element to be appended to this list

Returns:boolean

true (as specified by Collection#add)

Annotations
@Override
addback to summary
public void add(int index, E element)

Implements java.util.List.add.

Doc from java.util.List.add.

Inserts the specified element at the specified position in this list (optional operation). Shifts the element currently at that position (if any) and any subsequent elements to the right (adds one to their indices).

Parameters
index:int

index at which the specified element is to be inserted

element:E

element to be inserted

Annotations
@Override
addAllback to summary
public boolean addAll(Collection<? extends E> c)

Implements java.util.List.addAll.

Doc from java.util.List.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 (optional operation). The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. (Note that this will occur if the specified collection is this list, and it's nonempty.)

Parameters
c:Collection<? extends E>

collection containing elements to be added to this list

Returns:boolean

true if this list changed as a result of the call

Annotations
@Override
addAllback to summary
public boolean addAll(int index, Collection<? extends E> col)

Implements java.util.List.addAll.

Doc from java.util.List.addAll.

Inserts all of the elements in the specified collection into this list at the specified position (optional operation). 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 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. (Note that this will occur if the specified collection is this list, and it's nonempty.)

Parameters
index:int

index at which to insert the first element from the specified collection

col:Collection<? extends E>

collection containing elements to be added to this list

Returns:boolean

true if this list changed as a result of the call

Annotations
@Override
addIfAbsentback to summary
public void addIfAbsent(E e)
asTypedArrayback to summary
public E[] asTypedArray()

Return an array of type E[]. The returned array is intended to be iterated over. If the list is modified, subsequent calls to this method will return different/modified array instances.

clearback to summary
public void clear()

Implements java.util.List.clear.

Doc from java.util.List.clear.

Removes all of the elements from this list (optional operation). The list will be empty after this call returns.

Annotations
@Override
containsback to summary
public boolean contains(Object o)

Implements java.util.List.contains.

Doc from java.util.List.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 Objects.equals(o, e).

Parameters
o:Object

element whose presence in this list is to be tested

Returns:boolean

true if this list contains the specified element

Annotations
@Override
containsAllback to summary
public boolean containsAll(Collection<?> c)

Implements java.util.List.containsAll.

Doc from java.util.List.containsAll.

Returns true if this list contains all of the elements of the specified collection.

Parameters
c:Collection<?>

collection to be checked for containment in this list

Returns:boolean

true if this list contains all of the elements of the specified collection

Annotations
@Override
getback to summary
public E get(int index)

Implements java.util.List.get.

Doc from java.util.List.get.

Returns the element at the specified position in this list.

Parameters
index:int

index of the element to return

Returns:E

the element at the specified position in this list

Annotations
@Override
indexOfback to summary
public int indexOf(Object o)

Implements java.util.List.indexOf.

Doc from java.util.List.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 Objects.equals(o, get(i)), or -1 if there is no such index.

Parameters
o:Object

element to search for

Returns:int

the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element

Annotations
@Override
isEmptyback to summary
public boolean isEmpty()

Implements java.util.List.isEmpty.

Doc from java.util.List.isEmpty.

Returns true if this list contains no elements.

Returns:boolean

true if this list contains no elements

Annotations
@Override
isFreshback to summary
private boolean isFresh()
iteratorback to summary
public Iterator<E> iterator()

Implements java.util.List.iterator.

Doc from java.util.List.iterator.

Returns an iterator over the elements in this list in proper sequence.

Returns:Iterator<E>

an iterator over the elements in this list in proper sequence

Annotations
@Override
lastIndexOfback to summary
public int lastIndexOf(Object o)

Implements java.util.List.lastIndexOf.

Doc from java.util.List.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 Objects.equals(o, get(i)), or -1 if there is no such index.

Parameters
o:Object

element to search for

Returns:int

the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element

Annotations
@Override
listIteratorback to summary
public ListIterator<E> listIterator()

Implements java.util.List.listIterator.

Doc from java.util.List.listIterator.

Returns a list iterator over the elements in this list (in proper sequence).

Returns:ListIterator<E>

a list iterator over the elements in this list (in proper sequence)

Annotations
@Override
listIteratorback to summary
public ListIterator<E> listIterator(int index)

Implements java.util.List.listIterator.

Doc from java.util.List.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 to next. An initial call to previous would return the element with the specified index minus one.

Parameters
index:int

index of the first element to be returned from the list iterator (by a call to next)

Returns:ListIterator<E>

a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list

Annotations
@Override
markAsStaleback to summary
private void markAsStale()
refreshCopyback to summary
private void refreshCopy()
refreshCopyIfNecessaryback to summary
private void refreshCopyIfNecessary()
removeback to summary
public boolean remove(Object o)

Implements java.util.List.remove.

Doc from java.util.List.remove.

Removes the first occurrence of the specified element from this list, if it is present (optional operation). If this list does not contain the element, it is unchanged. More formally, removes the element with the lowest index i such that Objects.equals(o, 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).

Parameters
o:Object

element to be removed from this list, if present

Returns:boolean

true if this list contained the specified element

Annotations
@Override
removeback to summary
public E remove(int index)

Implements java.util.List.remove.

Doc from java.util.List.remove.

Removes the element at the specified position in this list (optional operation). Shifts any subsequent elements to the left (subtracts one from their indices). Returns the element that was removed from the list.

Parameters
index:int

the index of the element to be removed

Returns:E

the element previously at the specified position

Annotations
@Override
removeAllback to summary
public boolean removeAll(Collection<?> col)

Implements java.util.List.removeAll.

Doc from java.util.List.removeAll.

Removes from this list all of its elements that are contained in the specified collection (optional operation).

Parameters
col:Collection<?>

collection containing elements to be removed from this list

Returns:boolean

true if this list changed as a result of the call

Annotations
@Override
retainAllback to summary
public boolean retainAll(Collection<?> col)

Implements java.util.List.retainAll.

Doc from java.util.List.retainAll.

Retains only the elements in this list that are contained in the specified collection (optional operation). In other words, removes from this list all of its elements that are not contained in the specified collection.

Parameters
col:Collection<?>

collection containing elements to be retained in this list

Returns:boolean

true if this list changed as a result of the call

Annotations
@Override
setback to summary
public E set(int index, E element)

Implements java.util.List.set.

Doc from java.util.List.set.

Replaces the element at the specified position in this list with the specified element (optional operation).

Parameters
index:int

index of the element to replace

element:E

element to be stored at the specified position

Returns:E

the element previously at the specified position

Annotations
@Override
sizeback to summary
public int size()

Implements java.util.List.size.

Doc from java.util.List.size.

Returns the number of elements in this list. If this list contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.

Returns:int

the number of elements in this list

Annotations
@Override
subListback to summary
public List<E> subList(int fromIndex, int toIndex)

Implements java.util.List.subList.

Doc from java.util.List.subList.

Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive. (If fromIndex and toIndex 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 supported by this list.

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 for indexOf and lastIndexOf, and all of the algorithms in the Collections 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.)

Parameters
fromIndex:int

low endpoint (inclusive) of the subList

toIndex:int

high endpoint (exclusive) of the subList

Returns:List<E>

a view of the specified range within this list

Annotations
@Override
toArrayback to summary
public Object[] toArray()

Implements java.util.List.toArray.

Doc from java.util.List.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 even if this list is backed by an array). The caller is thus free to modify the returned array.

This method acts as bridge between array-based and collection-based APIs.

Returns:Object[]

an array containing all of the elements in this list in proper sequence

Annotations
@Override
toArrayback to summary
public <T> T[] toArray(T[] a)

Implements java.util.List.toArray.

Doc from java.util.List.toArray.

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 list 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.)

Like the toArray() method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.

Suppose x is a list known to contain only strings. The following code can be used to dump the list into a newly allocated array of String: 

String[] y = x.toArray(new String[0]);
Note that toArray(new Object[0]) is identical in function to toArray().
Parameters
<T>

Doc from java.util.Collection.toArray. the component type of the array to contain the collection

a:T[]

the array into which the elements of this 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:T[]

an array containing the elements of this list

Annotations
@SuppressWarnings:unchecked
@Override