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Class com.sun.java.util.collections.ArrayList
java.lang.Object
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+----com.sun.java.util.collections.AbstractCollection
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+----com.sun.java.util.collections.AbstractList
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+----com.sun.java.util.collections.ArrayList
- public class ArrayList
- extends AbstractList
- implements List, Cloneable, Serializable
Resizable-array implementation of the List interface. Implements
all optional list operations, and permits all elements, including
null. In addition to implementing the List interface,
this class provides methods to manipulate the size of the array that is
used internally to store the list. (This class is roughly equivalent to
Vector, except that it is unsynchronized.)
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 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 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.
- See Also:
- Collection, List, LinkedList, Vector, synchronizedList
-
ArrayList()
- Constructs an empty list.
-
ArrayList(Collection)
- Constructs a list containing the elements of the specified
collection, in the order they are returned by the collection's
iterator.
-
ArrayList(int)
- Constructs an empty list with the specified initial capacity.
-
add(int, Object)
- Inserts the specified element at the specified position in this
list.
-
add(Object)
- Appends the specified element to the end of this list.
-
addAll(Collection)
- 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.
-
addAll(int, Collection)
- Inserts all of the elements in the specified Collection into this
list, starting at the specified position.
-
clear()
- Removes all of the elements from this list.
-
clone()
- Returns a shallow copy of this ArrayList instance.
-
contains(Object)
- Returns true if this list contains the specified element.
-
ensureCapacity(int)
- 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.
-
get(int)
- Returns the element at the specified position in this list.
-
indexOf(Object)
- Searches for the first occurence of the given argument, testing
for equality using the equals method.
-
isEmpty()
- Tests if this list has no elements.
-
lastIndexOf(Object)
- Returns the index of the last occurrence of the specified object in
this list.
-
remove(int)
- Removes the element at the specified position in this list.
-
removeRange(int, int)
- Removes from this List all of the elements whose index is between
fromIndex, inclusive and toIndex, exclusive.
-
set(int, Object)
- Replaces the element at the specified position in this list with
the specified element.
-
size()
- Returns the number of elements in this list.
-
toArray()
- Returns an array containing all of the elements in this list
in the correct order.
-
toArray(Object[])
- Returns an array containing all of the elements in this list in the
correct order.
-
trimToSize()
- Trims the capacity of this ArrayList instance to be the
list's current size.
ArrayList
public ArrayList(int initialCapacity)
- Constructs an empty list with the specified initial capacity.
- Parameters:
- initialCapacity - the initial capacity of the list.
ArrayList
public ArrayList()
- Constructs an empty list.
ArrayList
public ArrayList(Collection c)
- Constructs a list containing the elements of the specified
collection, in the order they are returned by the collection's
iterator. The ArrayList instance has an initial capacity of
110% the size of the specified collection.
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.
size
public int size()
- Returns the number of elements in this list.
- Returns:
- the number of elements in this list.
- Overrides:
- size in class AbstractCollection
isEmpty
public boolean isEmpty()
- Tests if this list has no elements.
- Returns:
- true if this list has no elements;
false otherwise.
- Overrides:
- isEmpty in class AbstractCollection
contains
public boolean contains(Object elem)
- Returns true if this list contains the specified element.
- Parameters:
- o - element whose presence in this List is to be tested.
- Overrides:
- contains in class AbstractCollection
indexOf
public int indexOf(Object elem)
- Searches for the first occurence of the given argument, testing
for equality using the equals method.
- Parameters:
- elem - an object.
- Returns:
- the index of the first occurrence of the argument in this
list; returns -1 if the object is not found.
- Overrides:
- indexOf in class AbstractList
- See Also:
- equals
lastIndexOf
public int lastIndexOf(Object elem)
- Returns the index of the last occurrence of the specified object in
this list.
- Parameters:
- elem - the desired element.
- Returns:
- the index of the last occurrence of the specified object in
this list; returns -1 if the object is not found.
- Overrides:
- lastIndexOf in class AbstractList
clone
public Object clone()
- Returns a shallow copy of this ArrayList instance. (The
elements themselves are not copied.)
- Returns:
- a clone of this ArrayList instance.
- Overrides:
- clone in class Object
toArray
public Object[] toArray()
- Returns an array containing all of the elements in this list
in the correct order.
- Returns:
- an array containing all of the elements in this list
in the correct order.
- Overrides:
- toArray in class AbstractCollection
toArray
public Object[] toArray(Object a[])
- Returns an array containing all of the elements in this list in the
correct order. 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.
- 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.
- Overrides:
- toArray in class AbstractCollection
get
public Object get(int index)
- Returns the element at the specified position in this list.
- Parameters:
- index - index of element to return.
- Returns:
- the element at the specified position in this list.
- Overrides:
- get in class AbstractList
set
public Object set(int index,
Object element)
- Replaces the element at the specified position in this list with
the specified element.
- Parameters:
- index - index of element to replace.
- element - element to be stored at the specified position.
- Returns:
- the element previously at the specified position.
- Overrides:
- set in class AbstractList
add
public boolean add(Object o)
- Appends the specified element to the end of this list.
- Parameters:
- o - element to be appended to this list.
- Returns:
- true (as per the general contract of Collection.add).
- Overrides:
- add in class AbstractList
add
public void add(int index,
Object element)
- 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).
- Parameters:
- index - index at which the specified element is to be inserted.
- element - element to be inserted.
- Overrides:
- add in class AbstractList
remove
public Object remove(int index)
- Removes the element at the specified position in this list.
Shifts any subsequent elements to the left (subtracts one from their
indices).
- Parameters:
- index - the index of the element to removed.
- Returns:
- the element that was removed from the list.
- Overrides:
- remove in class AbstractList
clear
public void clear()
- Removes all of the elements from this list. The list will
be empty after this call returns.
- Overrides:
- clear in class AbstractList
addAll
public boolean addAll(Collection 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. 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.)
- Parameters:
- index - index at which to insert first element
from the specified collection.
- c - elements to be inserted into this list.
- Overrides:
- addAll in class AbstractCollection
addAll
public boolean addAll(int index,
Collection c)
- 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.
- Parameters:
- index - index at which to insert first element
from the specified collection.
- c - elements to be inserted into this list.
- Overrides:
- addAll in class AbstractList
removeRange
protected void removeRange(int fromIndex,
int toIndex)
- Removes from this List all of the elements whose index is between
fromIndex, inclusive and toIndex, exclusive. Shifts any succeeding
elements to the left (reduces their index).
This call shortens the list by (toIndex - fromIndex) elements.
(If toIndex==fromIndex, this operation has no effect.)
- Parameters:
- fromIndex - index of first element to be removed.
- fromIndex - index after last element to be removed.
- Overrides:
- removeRange in class AbstractList
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