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FlexDoc/Javadoc 2.0 Demo Java Doc |
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.
Field Summary |
Fields inherited from class java.util.AbstractList |
Constructor Summary |
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Constructs an empty list with an initial capacity of ten.
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Constructs a list containing the elements of the specified
collection, in the order they are returned by the collection's
iterator.
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ArrayList(int initialCapacity)
Constructs an empty list with the specified initial capacity.
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Method Summary |
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boolean |
Appends the specified element to the end of this list.
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void |
Inserts the specified element at the specified position in this
list.
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boolean |
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.
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boolean |
Inserts all of the elements in the specified collection into this
list, starting at the specified position.
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void |
clear()
Removes all of the elements from this list.
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clone()
Returns a shallow copy of this ArrayList instance.
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boolean |
Returns true if this list contains the specified element.
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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.
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boolean |
Compares the specified object with this list for equality.
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void |
Performs the given action for each element of the Iterable
until all elements have been processed or the action throws an
exception.
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get(int index)
Returns the element at the specified position in this list.
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int |
hashCode()
Returns the hash code value for this list.
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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.
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boolean |
isEmpty()
Returns true if this list contains no elements.
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iterator()
Returns an iterator over the elements in this list in proper sequence.
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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.
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Returns a list iterator over the elements in this list (in proper
sequence).
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listIterator(int index)
Returns a list iterator over the elements in this list (in proper
sequence), starting at the specified position in the list.
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remove(int index)
Removes the element at the specified position in this list.
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boolean |
Removes the first occurrence of the specified element from this list,
if it is present.
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boolean |
removeAll(Collection<?> c)
Removes from this list all of its elements that are contained in the
specified collection.
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boolean |
Removes all of the elements of this collection that satisfy the given
predicate.
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protected void |
removeRange(int fromIndex, int toIndex)
Removes from this list all of the elements whose index is between
fromIndex, inclusive, and toIndex, exclusive.
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void |
Replaces each element of this list with the result of applying the
operator to that element.
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boolean |
retainAll(Collection<?> c)
Retains only the elements in this list that are contained in the
specified collection.
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Replaces the element at the specified position in this list with
the specified element.
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int |
size()
Returns the number of elements in this list.
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void |
Sorts this list according to the order induced by the specified
Comparator.
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Creates a late-binding
and fail-fast Spliterator over the elements in this
list.
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subList(int fromIndex, int toIndex)
Returns a view of the portion of this list between the specified
fromIndex, inclusive, and toIndex, exclusive.
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Object[] |
toArray()
Returns an array containing all of the elements in this list
in proper sequence (from first to last element).
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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.
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void |
Trims the capacity of this ArrayList instance to be the
list's current size.
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Methods inherited from class java.util.AbstractCollection |
Methods inherited from class java.lang.Object |
Methods inherited from interface java.util.Collection |
Methods inherited from interface java.util.List |
public ArrayList |
(int initialCapacity) |
public ArrayList |
() |
public ArrayList |
(Collection<? extends E> c) |
public void trimToSize |
() |
public void ensureCapacity |
(int minCapacity) |
public int size |
() |
public boolean isEmpty |
() |
public boolean contains |
(Object o) |
public int indexOf |
(Object o) |
public int lastIndexOf |
(Object o) |
public Object clone |
() |
public Object[] toArray |
() |
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.
(T[] a) |
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.)
public E get |
(int index) |
public E set |
(int index, E element) |
public boolean add |
(E e) |
public void add |
(int index, E element) |
public E remove |
(int index) |
public boolean equals |
(Object o) |
public int hashCode |
() |
public boolean remove |
(Object o) |
public void clear |
() |
public boolean addAll |
(Collection<? extends E> c) |
public boolean addAll |
protected void removeRange |
(int fromIndex, int toIndex) |
public boolean removeAll |
(Collection<?> c) |
public boolean retainAll |
(Collection<?> c) |
(int index) |
The returned list iterator is fail-fast.
() |
The returned list iterator is fail-fast.
() |
The returned iterator is fail-fast.
(int fromIndex, int toIndex) |
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(Object) and lastIndexOf(Object), 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.)
public void forEach |
The behavior of this method is unspecified if the action performs side-effects that modify the underlying source of elements, unless an overriding class has specified a concurrent modification policy.
() |
The Spliterator reports Spliterator.SIZED, Spliterator.SUBSIZED, and Spliterator.ORDERED. Overriding implementations should document the reporting of additional characteristic values.
public boolean removeIf |
public void replaceAll |
(UnaryOperator<E> operator) |
public void sort |
(Comparator<? super E> c) |
All elements in this list must be mutually comparable using the specified comparator (that is, c.compare(e1, e2) must not throw a ClassCastException for any elements e1 and e2 in the list).
If the specified comparator is null then all elements in this list must implement the Comparable interface and the elements' natural ordering should be used.
This list must be modifiable, but need not be resizable.
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FlexDoc/Javadoc 2.0 Demo Java Doc |