A Vector, like an array, contains items that can be accessed using an integer
index. However, the size of a Vector can grow and shrink as needed to accommodate adding and removing items after the Vector has been created.
public classVectorimplements Cloneable { protected Object[]elementData; protected intelementCount; protected intcapacityIncrement; publicVector(int initialCapacity, int capacityIncrement); publicVector(int initialCapacity); publicVector(); public final StringtoString(); public Objectclone(); public final ObjectelementAt(int index) throwsIndexOutOfBoundsException; public final voidsetElementAt(Object obj, int index) throwsIndexOutOfBoundsException; public final ObjectfirstElement() throws NoSuchElementException; public final ObjectlastElement() throws NoSuchElementException; public final voidaddElement(Object obj); public final voidinsertElementAt(Object obj, int index) throwsIndexOutOfBoundsException; public final booleanremoveElement(Object obj); public final voidremoveElementAt(int index) throwsIndexOutOfBoundsException; public final voidremoveAllElements(); public final booleanisEmpty(); public final intsize(); public final voidsetSize(int newSize); public final intcapacity(); public final voidensureCapacity(int minCapacity); public final voidtrimToSize(); public final voidcopyInto(Object anArray[]) throwsIndexOutOfBoundsException; public final Enumerationelements(); public final booleancontains(Object elem); public final intindexOf(Object elem); public final intindexOf(Object elem, int index) throwsIndexOutOfBoundsException; public final intlastIndexOf(Object elem); public final intlastIndexOf(Object elem, int index) throwsIndexOutOfBoundsException; }
21.11.1 protected Object[] elementData;
Internally, a Vector keeps its elements in an array that is at least large enough to
contain all the elements.
21.11.2 protected int elementCount;
This field holds the number of items currently in this Vector object. Components
elementData[0] through elementData[elementCount-1] are the actual items.
21.11.3 protected int capacityIncrement;
When the method ensureCapacity (§21.11.22) must increase the size of the data
array in the field elementData (by creating a new array), it increases the size by
at least the amount in capacityIncrement; but if capacityIncrement is zero,
then it at least doubles the size of the data array.
21.11.4 public Vector(int initialCapacity, int capacityIncrement)
This constructor initializes a newly created Vector so that its internal data array
has size initialCapacity and its standard capacity increment is the value of
capacityIncrement. Initially, the Vector contains no items.
21.11.5 public Vector(int initialCapacity)
This constructor initializes a newly created Vector so that its internal data array
has size initialCapacity and its standard capacity increment is zero. Initially,
the Vector contains no items.
21.11.6 public Vector()
This constructor initializes a newly created Vector so that its internal data array
has size 10 and its standard capacity increment is zero. Initially the Vector contains no items.
21.11.7 public final String toString()
This Vector is represented in string form as a list of its items, enclosed in ASCII
square brackets and separated by the ASCII characters ", " (comma and space).
The toString method is used to convert the items to strings; a null reference is
rendered as the string "null".
Vector v = new Vector();
v.addElement("Canberra");
v.addElement("Cancun");
v.addElement("Canandaigua");
System.out.println(v.toString());
[Canberra, Cancun, Canandaigua]
Overrides the toString method of Object (§20.1.2).
21.11.8 public Object clone()
A copy of this Vector is constructed and returned. The copy will contains a reference to a clone of the internal data array, not a reference to the original internal
data array of this Vector.
Overrides the clone method of Object (§20.1.5).
21.11.9 public final Object elementAt(int index)
throws IndexOutOfBoundsException
The item of this Vector with the specified index is returned.
If the index is negative or not less than the current size of this Vector, an IndexOutOfBoundsException is thrown.
21.11.10 public final void setElementAt(Object obj, int index)
throws IndexOutOfBoundsException
The item of this Vector with the specified index is replaced with obj, so that obj
is now the item at the specified index within this Vector.
If the index is negative or not less than the current size of this Vector, an IndexOutOfBoundsException is thrown.
21.11.11 public final Object firstElement()
throws NoSuchElementException
If this Vector is empty, a NoSuchElementException is thrown. Otherwise, the
first item (the item at index 0) is returned.
21.11.12 public final Object lastElement()
throws NoSuchElementException
If this Vector is empty, a NoSuchElementException is thrown. Otherwise, the
last item (the item at index size()-1) is returned.
21.11.13 public final void addElement(Object obj)
The size of this Vector is increased by 1 and obj becomes the new last item.
21.11.14 public final void insertElementAt(Object obj, int index)
throws IndexOutOfBoundsException
The size of this Vector is increased by 1 and obj becomes the new item at the
specified index. Any item in this Vector that was previously at index k is first
moved to index k+1 if and only if k is not less than index.
21.11.15 public final boolean removeElement(Object obj)
If this Vector contains an occurrence of obj, then the first (lowest-indexed) such
occurrence is removed, as if by the method removeElementAt (§21.11.16), and
true is returned. If this Vector contains no occurrence of obj, this Vector is not
modified and false is returned.
21.11.16 public final void removeElementAt(int index)
throws IndexOutOfBoundsException
The size of this Vector is decreased by 1 and the item at the specified index is
removed from this Vector. Any item in this Vector that was previously at index
k is first moved to index k-1 if and only if k is greater than index.
21.11.17 public final void removeAllElements()
All elements are removed from this Vector, making it empty.
21.11.18 public final boolean isEmpty()
The result is true if and only if this Vector is empty, that is, its size is zero.
21.11.19 public final int size()
The size of this Vector (the number of items it currently contains) is returned.
21.11.20 public final void setSize(int newSize)
The size of this Vector is changed to newSize. If the new size is smaller than the
old size, then items are removed from the end and discarded. If the new size is
larger than the old size, then the new items are set to null.
21.11.21 public final int capacity()
The current capacity of this Vector (the length of its internal data array, kept in
the field elementData) is returned.
21.11.22 public final 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
(§21.11.1), with a larger one. The size of the new data array will be the old size
plus capacityIncrement (§21.11.3), unless the value of capacityIncrement is
nonpositive, 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.
21.11.23 public final void trimToSize()
If the capacity of this Vector is larger than its current size (§21.11.19), then the
capacity is changed to equal the size by replacing its internal data array, kept in
the field elementData, with a smaller one.
21.11.24 public final void copyInto(Object anArray[])
throws IndexOutOfBoundsException
All the items in this Vector are copied into the array anArray. The item at index
k in this Vector is copied into component k of anArray. If the length of anArray
is smaller than the size of this Vector, an IndexOutOfBoundsException is
thrown.
21.11.25 public final Enumeration elements()
An Enumeration (§21.1) is returned that 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.
21.11.26 public final boolean contains(Object elem)
The result is true if and only if some item in this Vector is the same as elem, as
determined by the equals method (§20.1.3).
21.11.27 public final int indexOf(Object elem)
If an item equal to elem is in this Vector, then the index of the first such occurrence is returned, that is, the smallest value k such that:
elem.equals(elementData[k])
is true. If no such item occurs in this Vector, then -1 is returned.
21.11.28 public final int indexOf(Object elem, int index)
throws IndexOutOfBoundsException
If an item equal to elem is in this Vector at position k or higher, then the index of
the first such occurrence is returned, that is, the smallest value k such that:
elem.equals(elementData[k]) && (k >= index)
is true. If no such item occurs in this Vector, then -1 is returned.
21.11.29 public final int lastIndexOf(Object elem)
If an item equal to elem is in this Vector, then the index of the last such occurrence is returned, that is, the largest value k such that:
elem.equals(elementData[k])
is true. If no such item occurs in this Vector, then -1 is returned.
21.11.30 public final int lastIndexOf(Object elem, int index)
throws IndexOutOfBoundsException
If an item equal to elem is in this Vector at position k or lower, then the index of
the last such occurrence is returned, that is, the largest value k such that:
elem.equals(elementData[k]) && (k <= index)
is true. If no such item occurs in this Vector, then -1 is returned.