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Java Platform 1.2 Beta 4 |
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SUMMARY: INNER | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
java.lang.Object | +--java.util.AbstractCollection | +--java.util.AbstractList | +--java.util.ArrayList
The size, isEmpty, get, set, iterator, and listIterator operations run in constant time. The add() operation runs in constant time unless it causes the ArrayList to exceed its capacity, in which case it runs in linear time. All of the other operations run in linear time (roughly speaking). The constant factor is low compared to that for LinkedList.
Each ArrayList 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 an ArrayList, its
capacity grows automatically. The details of the growth policy are not
specified beyond the fact that adding an element to an ArrayList has
constant amortized cost, that is, adding n elements requires O(n)
time. An application can increase the capacity of an ArrayList before
adding a large number of components 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 concurrently, and at least one of the threads modifies the ArrayList 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 ArrayList. If no such object exists, the ArrayList should be "wrapped" using the Collections.synchronizedList method. This is best done at creation time, to prevent accidental unsynchronized access to the ArrayList:
List list = Collections.synchronizedList(new ArrayList(...));
The Iterators returned by ArrayList's iterator and listIterator methods are fail-fast: if the ArrayList 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.
Collection
,
List
,
LinkedList
,
Vector
,
Collections.synchronizedList(List)
, Serialized FormFields inherited from class java.util.AbstractList | |
modCount |
Constructor Summary | |
ArrayList()
Constructs an empty ArrayList. |
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ArrayList(Collection c)
Constructs an ArrayList 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 ArrayList with the specified initial capacity. |
Method Summary | |
void | add(int index,
Object element)
Inserts the specified element at the specified position in this ArrayList. |
boolean | add(Object o)
Appends the specified element to the end of this ArrayList. |
boolean | addAll(Collection c)
Appends all of the elements in the specified Collection to the end of this this ArrayList, in the order that they are returned by the specified Collection's Iterator. |
boolean | addAll(int index,
Collection c)
Inserts all of the elements in the specified Collection into this ArrayList, starting at the specified position. |
void | clear()
Removes all of the elements from this ArrayList. |
Object | clone()
Returns a shallow copy of this ArrayList. |
boolean | contains(Object elem)
Returns true if this ArrayList contains the specified element. |
void | ensureCapacity(int minCapacity)
Increases the capacity of this ArrayList, if necessary, to ensure that it can hold at least the number of components specified by the minimum capacity argument. |
Object | get(int index)
Returns the element at the specified position in this ArrayList. |
int | indexOf(Object elem)
Searches for the first occurence of the given argument, testing for equality using the equals method. |
boolean | isEmpty()
Tests if this ArrayList has no components. |
int | lastIndexOf(Object elem)
Returns the index of the last occurrence of the specified object in this ArrayList. |
Object | remove(int index)
Removes the element at the specified position in this ArrayList. |
Object | set(int index,
Object element)
Replaces the element at the specified position in this ArrayList with the specified element. |
int | size()
Returns the number of components in this ArrayList. |
Object[] | toArray()
Returns an array containing all of the elements in this ArrayList in the correct order. |
Object[] | toArray(Object[] a)
Returns an array containing all of the elements in this ArrayList in the correct order. |
void | trimToSize()
Trims the capacity of this ArrayList to be the ArrayList's current size. |
Methods inherited from class java.util.AbstractList | |
equals , hashCode , iterator , listIterator , listIterator , subList |
Methods inherited from class java.util.AbstractCollection | |
containsAll , remove , removeAll , retainAll , toString |
Methods inherited from class java.lang.Object | |
finalize , getClass , notify , notifyAll , wait , wait , wait |
Constructor Detail |
public ArrayList(int initialCapacity)
initialCapacity
- the initial capacity of the ArrayList.public ArrayList()
public ArrayList(Collection c)
Method Detail |
public void trimToSize()
public void ensureCapacity(int minCapacity)
minCapacity
- the desired minimum capacity.public int size()
public boolean isEmpty()
true
if this ArrayList has no components;
false
otherwise.public boolean contains(Object elem)
o
- element whose presence in this List is to be tested.public int indexOf(Object elem)
equals
method.
elem
- an object.-1
if the object is not found.Object.equals(Object)
public int lastIndexOf(Object elem)
elem
- the desired component.public Object clone()
public Object[] toArray()
public Object[] toArray(Object[] a)
If the ArrayList fits in the specified array with room to spare (i.e., the array has more elements than the ArrayList), 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 ArrayList only if the caller knows that the ArrayList does not contain any null elements.
a
- the array into which the elements of the ArrayList are to
be stored, if it is big enough; otherwise, a new array of the
same runtime type is allocated for this purpose.public Object get(int index)
index
- index of element to return.public Object set(int index, Object element)
index
- index of element to replace.
element
- element to be stored at the specified position.public boolean add(Object o)
o
- element to be appended to this ArrayList.public void add(int index, Object element)
index
- index at which the specified element is to be inserted.
element
- element to be inserted.public Object remove(int index)
index
- the index of the element to removed.public void clear()
public boolean addAll(Collection c)
index
- index at which to insert first element
from the specified collection.
c
- elements to be inserted into this ArrayList.public boolean addAll(int index, Collection c)
index
- index at which to insert first element
from the specified collection.
c
- elements to be inserted into this ArrayList.
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Java Platform 1.2 Beta 4 |
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