public class java.util.ArrayList<A>

java.lang.Object
   |
   +----java.util.AbstractCollection<A>
           |
           +----java.util.AbstractList<A>
                   |
                   +----java.util.ArrayList<A>

public class ArrayList<A>
  extends AbstractList<A>
  implements List<A>, Cloneable, java.io.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, ArrayList provides methods to manipulate the size of the array that is used internally to store the List. (ArrayList is roughly equivalent to Vector, except that it is unsynchronized.)

The size, isEmpty, get, set, clear, 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 and a capacityIncrement. 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; it is usually larger because as components are added to the ArrayList, the ArrayList's storage increases in chunks the size of its capacityIncrement. (The capacityIncrement does not change over the lifetime of the ArrayList.) An application can increase the capacity of an ArrayList before inserting a large number of components; this reduces 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.synchronizedSet 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.

See also:

Collection, List, LinkedList, Vector, Collections.synchronizedList

ArrayList()

Constructs an empty ArrayList.

ArrayList(Collection<A>)

Constructs an ArrayList containing the elements of the specified Collection, in the order

ArrayList(int)

Constructs an empty ArrayList with the specified initial capacity.

ArrayList(int, int)

Constructs an empty ArrayList with the specified initial capacity and capacity

add(int, A)

Inserts the specified element at the specified position in this ArrayList

add(A)

Appends the specified element to the end of this ArrayList.

addAll(int, Collection<A>)

Inserts all of the elements in the specified Collection into this ArrayList, starting at

addAll(Collection<A>)

Appends all of the elements in the specified Collection to the end of this this

clear()

Removes all of the elements from this ArrayList

clone()

Returns a shallow copy of this ArrayList

contains(A)

Returns true if this ArrayList contains the specified element.

ensureCapacity(int)

Increases the capacity of this ArrayList, if necessary, to ensure that it can hold at

get(int)

Returns the element at the specified position in this ArrayList.

indexOf(A, int)

Searches for the first occurence of the given argument, beginning the search at

indexOf(A)

Searches for the first occurence of the given argument, testing for equality using the

isEmpty()

Tests if this ArrayList has no components.

lastIndexOf(A, int)

Searches backwards for the specified object, starting from the specified index, and

lastIndexOf(A)

Returns the index of the last occurrence of the specified object in this ArrayList.

remove(int)

Removes the element at the specified position in this ArrayList. Shifts any subsequent

removeRange(int, int)

Removes from this ArrayList all of the elements whose index is between fromIndex,

set(int, A)

Replaces the element at the specified position in this ArrayList with the specified

size()

Returns the number of components in this ArrayList.

toArray()

Returns an array containing all of the elements in this ArrayList in the correct order.

trimToSize()

Trims the capacity of this ArrayList to be the ArrayList's current size

public ArrayList(int initialCapacity,
                 int capacityIncrement);

Constructs an empty ArrayList with the specified initial capacity and capacity increment.

Parameters:

initialCapacity - the initial capacity of the ArrayList.

capacityIncrement - the amount by which the capacity is increased when the ArrayList overflows.

ArrayList

public ArrayList(int initialCapacity);

Constructs an empty ArrayList with the specified initial capacity.

Parameters:

initialCapacity - the initial capacity of the ArrayList.

ArrayList

public ArrayList();

Constructs an empty ArrayList.

ArrayList

public ArrayList(Collection<A> c);

Constructs an ArrayList containing the elements of the specified Collection, in the order they are returned by the Collection's iterator. The ArrayList has initial capacity of 110% the size of the specified Collection, and the default capacity increment.

public void trimToSize();

Trims the capacity of this ArrayList to be the ArrayList's current size. An application can use this operation to minimize the storage of an ArrayList.

ensureCapacity

public 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.

Parameters:

minCapacity - the desired minimum capacity.

size

public int size();

Returns the number of components in this ArrayList.

Returns:

the number of components in this ArrayList.

Overrides:

size in class AbstractCollection

isEmpty

public boolean isEmpty();

Tests if this ArrayList has no components.

Returns:

true if this ArrayList has no components; false otherwise.

Overrides:

isEmpty in class AbstractCollection

contains

public boolean contains(A elem);

Returns true if this ArrayList 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(A 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 ArrayList; returns -1 if the object is not found.

Overrides:

indexOf in class AbstractList

See also:

equals(Object)

indexOf

public int indexOf(A elem,
                   int index);

Searches for the first occurence of the given argument, beginning the search at index, and testing for equality using the equals method.

Parameters:

elem - an object.

index - the index to start searching from.

Returns:

the index of the first occurrence of the object argument in this ArrayList at position index or later in the ArrayList; returns -1 if the object is not found.

Overrides:

indexOf in class AbstractList

See also:

equals(Object)

lastIndexOf

public int lastIndexOf(A elem);

Returns the index of the last occurrence of the specified object in this ArrayList.

Parameters:

elem - the desired component.

Returns:

the index of the last occurrence of the specified object in this ArrayList; returns -1 if the object is not found.

Overrides:

lastIndexOf in class AbstractList

lastIndexOf

public int lastIndexOf(A elem,
                       int index);

Searches backwards for the specified object, starting from the specified index, and returns an index to it.

Parameters:

elem - the desired component.

index - the index to start searching from.

Returns:

the index of the last occurrence of the specified object in this ArrayList at position less than index in the ArrayList; -1 if the object is not found.

Overrides:

lastIndexOf in class AbstractList

clone

public Object clone();

Returns a shallow copy of this ArrayList. (The elements themselves are not copied.)

Returns:

a clone of this ArrayList.

Overrides:

clone in class Object

toArray

public Object[] toArray();

Returns an array containing all of the elements in this ArrayList in the correct order.

Overrides:

toArray in class AbstractCollection

get

public A get(int index);

Returns the element at the specified position in this ArrayList.

Parameters:

index - index of element to return.

Throws:

IndexOutOfBoundsException -index is out of range (index < 0 || index >= size()).

Overrides:

get in class AbstractList

set

public A set(int index,
             A element);

Replaces the element at the specified position in this ArrayList 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.

Throws:

IndexOutOfBoundsException -index out of range (index < 0 || index >= size()).

Overrides:

set in class AbstractList

add

public boolean add(A o);

Appends the specified element to the end of this ArrayList.

Parameters:

o - element to be appended to this ArrayList.

Returns:

true (as per the general contract of Collection.add).

Overrides:

add in class AbstractList

add

public void add(int index,
                A element);

Inserts the specified element at the specified position in this ArrayList. 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.

Throws:

IndexOutOfBoundsException -index is out of range (index < 0 || index > size()).

Overrides:

add in class AbstractList

remove

public A remove(int index);

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

Parameters:

index - the index of the element to removed.

Throws:

IndexOutOfBoundsException -index out of range (index < 0 || index >= size()).

Overrides:

remove in class AbstractList

clear

public void clear();

Removes all of the elements from this ArrayList. The ArrayList will be empty after this call returns, unless it throws an exception.

Throws:

UnsupportedOperationException -clear is not supported by this Set.

Overrides:

clear in class AbstractCollection

addAll

public boolean addAll(Collection<A> 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. 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 the specified Collection is this ArrayList, and this ArrayList is nonempty.)

Parameters:

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

c - elements to be inserted into this ArrayList.

Throws:

IndexOutOfBoundsException -index out of range (index < 0 || index > size()).

Overrides:

addAll in class AbstractCollection

removeRange

public void removeRange(int fromIndex,
                        int toIndex);

Removes from this ArrayList 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 ArrayList 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.

Throws:

IndexOutOfBoundsException -fromIndex or toIndex out of range (fromIndex < 0 || fromIndex >= size() || toIndex > size() || toIndex < fromIndex).

Overrides:

removeRange in class AbstractList

addAll

public boolean addAll(int index,
                      Collection<A> c);

Inserts all of the elements in the specified Collection into this ArrayList, 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 ArrayList 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 ArrayList.

Throws:

IndexOutOfBoundsException -index out of range (index < 0 || index > size()).

Overrides:

addAll in class AbstractList

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