public class Vector<E> extends AbstractList<E> implements List<E>, RandomAccess, Cloneable, Serializable
Vector class implements a growable array of objects. Like an array, it contains
components that can be accessed using an integer index. However, the size of a Vector can
grow or shrink as needed to accommodate adding and removing items after the Vector has
been created.
Each vector tries to optimize storage management by maintaining a capacity and a
capacityIncrement. The capacity is always at least as large as the vector size;
it is usually larger because as components are added to the vector, the vector's storage
increases in chunks the size of capacityIncrement. An application can increase the
capacity of a vector before inserting a large number of components; this reduces the amount of
incremental reallocation.
The iterators returned by this class's iterator() and
listIterator(int) methods are fail-fast: if the vector 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. The Enumerations returned by the elements method are not fail-fast.
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.
As of the Java 2 platform v1.2, this class was retrofitted to implement the List
interface, making it a member of the Java Collections Framework. Unlike the new collection
implementations, Vector is synchronized. If a thread-safe implementation is not needed,
it is recommended to use ArrayList in place of Vector.
Collection,
Serialized Form| Modifier and Type | Field and Description |
|---|---|
protected int |
capacityIncrement
The amount by which the capacity of the vector is automatically incremented when its size becomes
greater than its capacity.
|
protected int |
elementCount
The number of valid components in this
Vector object. |
protected Object[] |
elementData
The array buffer into which the components of the vector are stored.
|
modCount| Constructor and Description |
|---|
Vector()
Constructs an empty vector so that its internal data array has size
10 and its standard
capacity increment is zero. |
Vector(Collection<? extends E> c)
Constructs a vector containing the elements of the specified collection, in the order they are
returned by the collection's iterator.
|
Vector(int initialCapacity)
Constructs an empty vector with the specified initial capacity and with its capacity increment
equal to zero.
|
Vector(int initialCapacity,
int capacityIncrement)
Constructs an empty vector with the specified initial capacity and capacity increment.
|
| Modifier and Type | Method and Description |
|---|---|
boolean |
add(E e)
Appends the specified element to the end of this Vector.
|
void |
add(int index,
E element)
Inserts the specified element at the specified position in this Vector.
|
boolean |
addAll(Collection<? extends E> c)
Appends all of the elements in the specified Collection to the end of this Vector, 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 Vector at the specified
position.
|
void |
addElement(E obj)
Adds the specified component to the end of this vector, increasing its size by one.
|
int |
capacity()
Returns the current capacity of this vector.
|
void |
clear()
Removes all of the elements from this Vector.
|
Object |
clone()
Returns a clone of this vector.
|
boolean |
contains(Object o)
Returns
true if this vector contains the specified element. |
boolean |
containsAll(Collection<?> c)
Returns true if this Vector contains all of the elements in the specified Collection.
|
void |
copyInto(Object[] anArray)
Copies the components of this vector into the specified array.
|
E |
elementAt(int index)
Returns the component at the specified index.
|
Enumeration<E> |
elements()
Returns an enumeration of the components of this vector.
|
void |
ensureCapacity(int minCapacity)
Increases the capacity of this vector, if necessary, to ensure that it can hold at least the
number of components specified by the minimum capacity argument.
|
boolean |
equals(Object o)
Compares the specified Object with this Vector for equality.
|
E |
firstElement()
Returns the first component (the item at index
0) of this vector. |
E |
get(int index)
Returns the element at the specified position in this Vector.
|
int |
hashCode()
Returns the hash code value for this Vector.
|
int |
indexOf(Object o)
Returns the index of the first occurrence of the specified element in this vector, or -1 if this
vector does not contain the element.
|
int |
indexOf(Object o,
int index)
Returns the index of the first occurrence of the specified element in this vector, searching
forwards from
index, or returns -1 if the element is not found. |
void |
insertElementAt(E obj,
int index)
Inserts the specified object as a component in this vector at the specified
index. |
boolean |
isEmpty()
Tests if this vector has no components.
|
Iterator<E> |
iterator()
Returns a list iterator over the elements in this list (in proper sequence).
|
E |
lastElement()
Returns the last component of the vector.
|
int |
lastIndexOf(Object o)
Returns the index of the last occurrence of the specified element in this vector, or -1 if this
vector does not contain the element.
|
int |
lastIndexOf(Object o,
int index)
Returns the index of the last occurrence of the specified element in this vector, searching
backwards from
index, or returns -1 if the element is not found. |
ListIterator<E> |
listIterator()
Returns a list iterator over the elements in this list (in proper sequence), starting at the
specified position in the list.
|
ListIterator<E> |
listIterator(int index)
Returns a list iterator over the elements in this list (in proper sequence), starting at the
specified position in the list.
|
E |
remove(int index)
Removes the element at the specified position in this Vector.
|
boolean |
remove(Object o)
Removes the first occurrence of the specified element in this Vector If the Vector does not
contain the element, it is unchanged.
|
boolean |
removeAll(Collection<?> c)
Removes from this Vector all of its elements that are contained in the specified Collection.
|
void |
removeAllElements()
Removes all components from this vector and sets its size to zero.
|
boolean |
removeElement(Object obj)
Removes the first (lowest-indexed) occurrence of the argument from this vector.
|
void |
removeElementAt(int index)
Deletes the component at the specified index.
|
protected void |
removeRange(int fromIndex,
int toIndex)
Removes from this list all of the elements whose index is between
fromIndex, inclusive,
and toIndex, exclusive. |
boolean |
retainAll(Collection<?> c)
Retains only the elements in this Vector that are contained in the specified Collection.
|
E |
set(int index,
E element)
Replaces the element at the specified position in this Vector with the specified element.
|
void |
setElementAt(E obj,
int index)
Sets the component at the specified
index of this vector to be the specified object. |
void |
setSize(int newSize)
Sets the size of this vector.
|
int |
size()
Returns the number of components in this vector.
|
List<E> |
subList(int fromIndex,
int toIndex)
Returns a view of the portion of this List between fromIndex, inclusive, and toIndex, exclusive.
|
Object[] |
toArray()
Returns an array containing all of the elements in this Vector in the correct order.
|
<T> T[] |
toArray(T[] a)
Returns an array containing all of the elements in this Vector in the correct order; the runtime
type of the returned array is that of the specified array.
|
String |
toString()
Returns a string representation of this Vector, containing the String representation of each
element.
|
void |
trimToSize()
Trims the capacity of this vector to be the vector's current size.
|
protected int capacityIncrement
protected int elementCount
Vector object. Components elementData[0]
through elementData[elementCount-1] are the actual items.protected Object[] elementData
Any array elements following the last element in the Vector are null.
public Vector()
10 and its standard
capacity increment is zero.public Vector(Collection<? extends E> c)
c - the collection whose elements are to be placed into this vectorNullPointerException - if the specified collection is nullpublic Vector(int initialCapacity)
initialCapacity - the initial capacity of the vectorIllegalArgumentException - if the specified initial capacity is negativepublic Vector(int initialCapacity,
int capacityIncrement)
initialCapacity - the initial capacity of the vectorcapacityIncrement - the amount by which the capacity is increased when the vector overflowsIllegalArgumentException - if the specified initial capacity is negativepublic boolean add(E e)
add in interface Collection<E>add in interface List<E>add in class AbstractList<E>e - element to be appended to this Vectortrue (as specified by Collection.add(E))public void add(int index,
E element)
add in interface List<E>add in class AbstractList<E>index - index at which the specified element is to be insertedelement - element to be insertedArrayIndexOutOfBoundsException - if the index is out of range (index < 0 || index > size())public boolean addAll(Collection<? extends E> c)
addAll in interface Collection<E>addAll in interface List<E>addAll in class AbstractCollection<E>c - elements to be inserted into this Vectortrue if this Vector changed as a result of the callNullPointerException - if the specified collection is nullAbstractCollection.add(Object)public boolean addAll(int index,
Collection<? extends E> c)
addAll in interface List<E>addAll in class AbstractList<E>index - index at which to insert the first element from the specified collectionc - elements to be inserted into this Vectortrue if this Vector changed as a result of the callArrayIndexOutOfBoundsException - if the index is out of range (index < 0 || index > size())NullPointerException - if the specified collection is nullpublic void addElement(E obj)
This method is identical in functionality to the add(E) method (which is
part of the List interface).
obj - the component to be addedpublic int capacity()
elementData of this vector)public void clear()
clear in interface Collection<E>clear in interface List<E>clear in class AbstractList<E>public Object clone()
Vector object.public boolean contains(Object o)
true if this vector contains the specified element. More formally, returns
true if and only if this vector contains at least one element e such that
(o==null ? e==null : o.equals(e)).contains in interface Collection<E>contains in interface List<E>contains in class AbstractCollection<E>o - element whose presence in this vector is to be testedtrue if this vector contains the specified elementpublic boolean containsAll(Collection<?> c)
containsAll in interface Collection<E>containsAll in interface List<E>containsAll in class AbstractCollection<E>c - a collection whose elements will be tested for containment in this VectorNullPointerException - if the specified collection is nullAbstractCollection.contains(Object)public void copyInto(Object[] anArray)
k in
this vector is copied into component k of anArray.anArray - the array into which the components get copiedNullPointerException - if the given array is nullIndexOutOfBoundsException - if the specified array is not large enough to hold all the components of this vectorArrayStoreException - if a component of this vector is not of a runtime type that can be stored in the
specified arraytoArray(Object[])public E elementAt(int index)
This method is identical in functionality to the get(int) method (which is part of the
List interface).
index - an index into this vectorArrayIndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())public Enumeration<E> elements()
Enumeration object
will generate all items in this vector. The first item generated is the item at index 0,
then the item at index 1, and so on.Iteratorpublic void ensureCapacity(int minCapacity)
If the current capacity of this vector is less than minCapacity, then its capacity is
increased by replacing its internal data array, kept in the field elementData, with a
larger one. The size of the new data array will be the old size plus capacityIncrement,
unless the value of capacityIncrement is less than or equal to zero, in which case the
new capacity will be twice the old capacity; but if this new size is still smaller than
minCapacity, then the new capacity will be minCapacity.
minCapacity - the desired minimum capacitypublic boolean equals(@Nullable Object o)
e1 and e2 are
equal if (e1==null ? e2==null :
e1.equals(e2)).) In other words, two Lists are defined to be equal if they contain the same
elements in the same order.equals in interface Collection<E>equals in interface List<E>equals in class AbstractList<E>o - the Object to be compared for equality with this VectorObject.hashCode(),
HashMappublic E firstElement()
0) of this vector.NoSuchElementException - if this vector has no componentspublic E get(int index)
get in interface List<E>get in class AbstractList<E>index - index of the element to returnArrayIndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())public int hashCode()
hashCode in interface Collection<E>hashCode in interface List<E>hashCode in class AbstractList<E>Object.equals(java.lang.Object),
System.identityHashCode(java.lang.Object)public int indexOf(Object o)
i such that
(o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no
such index.public int indexOf(Object o, int index)
index, or returns -1 if the element is not found. More formally, returns
the lowest index i such that
(i >= index && (o==null ? get(i)==null : o.equals(get(i))))
, or -1 if there is no such index.o - element to search forindex - index to start searching fromindex
or later in the vector; -1 if the element is not found.IndexOutOfBoundsException - if the specified index is negativeObject.equals(Object)public void insertElementAt(E obj, int index)
index. Each
component in this vector with an index greater or equal to the specified index is shifted
upward to have an index one greater than the value it had previously.
The index must be a value greater than or equal to 0 and less than or equal to the
current size of the vector. (If the index is equal to the current size of the vector, the new
element is appended to the Vector.)
This method is identical in functionality to the add(int, E) method
(which is part of the List interface). Note that the add method reverses the
order of the parameters, to more closely match array usage.
obj - the component to insertindex - where to insert the new componentArrayIndexOutOfBoundsException - if the index is out of range (index < 0 || index > size())public boolean isEmpty()
isEmpty in interface Collection<E>isEmpty in interface List<E>isEmpty in class AbstractCollection<E>true if and only if this vector has no components, that is, its size is zero;
false otherwise.public Iterator<E> iterator()
The returned list iterator is fail-fast.
iterator in interface Iterable<E>iterator in interface Collection<E>iterator in interface List<E>iterator in class AbstractList<E>listIterator(int)public E lastElement()
size() - 1.NoSuchElementException - if this vector is emptypublic int lastIndexOf(Object o)
i such that
(o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no
such index.lastIndexOf in interface List<E>lastIndexOf in class AbstractList<E>o - element to search forpublic int lastIndexOf(Object o, int index)
index, or returns -1 if the element is not found. More formally, returns
the highest index i such that
(i <= index && (o==null ? get(i)==null : o.equals(get(i))))
, or -1 if there is no such index.o - element to search forindex - index to start searching backwards fromindex in this vector; -1 if the element is not found.IndexOutOfBoundsException - if the specified index is greater than or equal to the current size of this vectorpublic ListIterator<E> listIterator()
next. An initial call to
previous would return the element with the specified index minus
one.
The returned list iterator is fail-fast.
listIterator in interface List<E>listIterator in class AbstractList<E>IndexOutOfBoundsException - if the index is out of range (index < 0 || index > size())AbstractList.listIterator(int)public ListIterator<E> listIterator(int index)
next. An initial call to
previous would return the element with the specified index minus
one.
The returned list iterator is fail-fast.
listIterator in interface List<E>listIterator in class AbstractList<E>index - index of the first element to be returned from the list iterator (by a call to
next)IndexOutOfBoundsException - if the index is out of range (index < 0 || index > size())public E remove(int index)
remove in interface List<E>remove in class AbstractList<E>index - the index of the element to be removedArrayIndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())
the index of the element to be removedpublic boolean remove(Object o)
(o==null ? get(i)==null : o.equals(get(i))) (if such an element exists).remove in interface Collection<E>remove in interface List<E>remove in class AbstractCollection<E>o - element to be removed from this Vector, if presentpublic boolean removeAll(Collection<?> c)
removeAll in interface Collection<E>removeAll in interface List<E>removeAll in class AbstractCollection<E>c - a collection of elements to be removed from the VectorClassCastException - if the types of one or more elements in this vector are incompatible with the specified
collection (optional)NullPointerException - if this vector contains one or more null elements and the specified collection does not
support null elements (optional), or
if the specified collection is nullAbstractCollection.remove(Object),
AbstractCollection.contains(Object)public void removeAllElements()
public boolean removeElement(Object obj)
This method is identical in functionality to the remove(Object) method (which is part of
the List interface).
obj - the component to be removedtrue if the argument was a component of this vector; false otherwise.public void removeElementAt(int index)
index is shifted downward to have an index one smaller than the
value it had previously. The size of this vector is decreased by 1.
The index must be a value greater than or equal to 0 and less than the current size of
the vector.
This method is identical in functionality to the remove(int) method (which is part of
the List interface). Note that the remove method returns the old value that was
stored at the specified position.
index - the index of the object to removeArrayIndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())protected void removeRange(int fromIndex,
int toIndex)
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.)removeRange in class AbstractList<E>fromIndex - index of first element to be removedtoIndex - index after last element to be removedpublic boolean retainAll(Collection<?> c)
retainAll in interface Collection<E>retainAll in interface List<E>retainAll in class AbstractCollection<E>c - a collection of elements to be retained in this Vector (all other elements are removed)ClassCastException - if the types of one or more elements in this vector are incompatible with the specified
collection (optional)NullPointerException - if this vector contains one or more null elements and the specified collection does not
support null elements (optional), or
if the specified collection is nullAbstractCollection.remove(Object),
AbstractCollection.contains(Object)public E set(int index, E element)
set in interface List<E>set in class AbstractList<E>index - index of the element to replaceelement - element to be stored at the specified positionArrayIndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())public void setElementAt(E obj, int index)
index of this vector to be the specified object. The
previous component at that position is discarded.
The index must be a value greater than or equal to 0 and less than the current size of
the vector.
This method is identical in functionality to the set(int, E) method
(which is part of the List interface). Note that the set method reverses the
order of the parameters, to more closely match array usage. Note also that the set method
returns the old value that was stored at the specified position.
obj - what the component is to be set toindex - the specified indexArrayIndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())public void setSize(int newSize)
null
items are added to the end of the vector. If the new size is less than the current size, all
components at index newSize and greater are discarded.newSize - the new size of this vectorArrayIndexOutOfBoundsException - if the new size is negativepublic int size()
size in interface Collection<E>size in interface List<E>size in class AbstractCollection<E>public List<E> subList(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 operating on 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 and lastIndexOf, 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 the List, or otherwise perturb it in such a fashion that iterations in progress may yield incorrect results.)
subList in interface List<E>subList in class AbstractList<E>fromIndex - low endpoint (inclusive) of the subListtoIndex - high endpoint (exclusive) of the subListIndexOutOfBoundsException - if an endpoint index value is out of range (fromIndex < 0 || toIndex > size)IllegalArgumentException - if the endpoint indices are out of order (fromIndex > toIndex)public Object[] toArray()
toArray in interface Collection<E>toArray in interface List<E>toArray in class AbstractCollection<E>public <T> T[] toArray(T[] a)
If the Vector fits in the specified array with room to spare (i.e., the array has more elements than the Vector), the element in the array immediately following the end of the Vector is set to null. (This is useful in determining the length of the Vector only if the caller knows that the Vector does not contain any null elements.)
toArray in interface Collection<E>toArray in interface List<E>toArray in class AbstractCollection<E>T - the runtime type of the array to contain the collectiona - the array into which the elements of the Vector are to be stored, if it is big enough;
otherwise, a new array of the same runtime type is allocated for this purpose.ArrayStoreException - if the runtime type of a is not a supertype of the runtime type of every element in this
VectorNullPointerException - if the given array is nullpublic String toString()
toString in class AbstractCollection<E>public void trimToSize()
elementData, with a smaller one. An application
can use this operation to minimize the storage of a vector.