public class

IdentityArrayList

extends AbstractList<E>
implements List<E> RandomAccess
java.lang.Object
   ↳ java.util.AbstractCollection<E>
     ↳ java.util.AbstractList<E>
       ↳ sun.awt.util.IdentityArrayList<E>

Class Overview

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 IdentityArrayList 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 IdentityArrayList, 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 IdentityArrayList 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 IdentityArrayList 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 Collections.synchronizedList method. This is best done at creation time, to prevent accidental unsynchronized access to the list:

   List list = Collections.synchronizedList(new IdentityArrayList(...));

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.

Summary

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Inherited Fields
From class java.util.AbstractList
Public Constructors
IdentityArrayList(int initialCapacity)
Constructs an empty list with the specified initial capacity.
IdentityArrayList()
Constructs an empty list with an initial capacity of ten.
IdentityArrayList(Collection<? extends E> c)
Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.
Public Methods
boolean add(E e)
Appends the specified element to the end of this list.
void add(int index, E element)
Inserts the specified element at the specified position in this list.
boolean addAll(Collection<? extends E> 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.
boolean addAll(int index, Collection<? extends E> c)
Inserts all of the elements in the specified collection into this list, starting at the specified position.
void clear()
Removes all of the elements from this list.
boolean contains(Object o)
Returns true if this list contains the specified element.
void ensureCapacity(int minCapacity)
Increases the capacity of this IdentityArrayList instance, if necessary, to ensure that it can hold at least the number of elements specified by the minimum capacity argument.
E get(int index)
Returns the element at the specified position in this list.
int indexOf(Object o)
Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
boolean isEmpty()
Returns true if this list contains no elements.
int lastIndexOf(Object o)
Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
E remove(int index)
Removes the element at the specified position in this list.
boolean remove(Object o)
Removes the first occurrence of the specified element from this list, if it is present.
E set(int index, E element)
Replaces the element at the specified position in this list with the specified element.
int size()
Returns the number of elements in this list.
<T> T[] toArray(T[] a)
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.
Object[] toArray()
Returns an array containing all of the elements in this list in proper sequence (from first to last element).
void trimToSize()
Trims the capacity of this IdentityArrayList instance to be the list's current size.
Protected Methods
void removeRange(int fromIndex, int toIndex)
Removes from this list all of the elements whose index is between fromIndex, inclusive, and toIndex, exclusive.
[Expand]
Inherited Methods
From class java.util.AbstractList
From class java.util.AbstractCollection
From class java.lang.Object
From interface java.lang.Iterable
From interface java.util.Collection
From interface java.util.List

Public Constructors

public IdentityArrayList (int initialCapacity)

Constructs an empty list with the specified initial capacity.

Parameters
initialCapacity the initial capacity of the list
Throws
IllegalArgumentException if the specified initial capacity is negative

public IdentityArrayList ()

Constructs an empty list with an initial capacity of ten.

public IdentityArrayList (Collection<? extends E> c)

Constructs a list containing the elements of the specified collection, in the order they are returned by the collection's iterator.

Parameters
c the collection whose elements are to be placed into this list
Throws
NullPointerException if the specified collection is null

Public Methods

public boolean add (E e)

Appends the specified element to the end of this list.

Parameters
e element to be appended to this list
Returns
  • true (as specified by add(E))

public void add (int index, E 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

public boolean addAll (Collection<? extends E> 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
c collection containing elements to be added to this list
Returns
  • true if this list changed as a result of the call
Throws
NullPointerException if the specified collection is null

public boolean addAll (int index, Collection<? extends E> 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 the first element from the specified collection
c collection containing elements to be added to this list
Returns
  • true if this list changed as a result of the call
Throws
IndexOutOfBoundsException
NullPointerException if the specified collection is null

public void clear ()

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

public boolean contains (Object o)

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 (o==null ? e==null : o == e).

Parameters
o element whose presence in this list is to be tested
Returns
  • true if this list contains the specified element

public void ensureCapacity (int minCapacity)

Increases the capacity of this IdentityArrayList 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

public E get (int index)

Returns the element at the specified position in this list.

Parameters
index index of the element to return
Returns
  • the element at the specified position in this list

public int indexOf (Object o)

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 (o==null ? get(i)==null : o == get(i)), or -1 if there is no such index.

Parameters
o element to search for
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 ()

Returns true if this list contains no elements.

Returns
  • true if this list contains no elements

public int lastIndexOf (Object o)

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 (o==null ? get(i)==null : o == get(i)), or -1 if there is no such index.

Parameters
o element to search for
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 E 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 be removed
Returns
  • the element that was removed from the list

public boolean remove (Object o)

Removes the first occurrence of the specified element from this list, if it is present. If the list does not contain the element, it is unchanged. More formally, removes the element with the lowest index i such that (o==null ? get(i)==null : 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 element to be removed from this list, if present
Returns
  • true if this list contained the specified element

public E set (int index, E element)

Replaces the element at the specified position in this list with the specified element.

Parameters
index index of the element to replace
element element to be stored at the specified position
Returns
  • the element previously at the specified position

public int size ()

Returns the number of elements in this list.

Returns
  • the number of elements in this list

public T[] toArray (T[] a)

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 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
Throws
ArrayStoreException if the runtime type of the specified array is not a supertype of the runtime type of every element in this list
NullPointerException if the specified array is null

public Object[] 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). The caller is thus free to modify the returned array.

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

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

public void trimToSize ()

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

Protected Methods

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
toIndex index after last element to be removed
Throws
IndexOutOfBoundsException if fromIndex or toIndex out of range (fromIndex < 0 || fromIndex >= size() || toIndex > size() || toIndex < fromIndex)