Vector implements a dynamic array. It is similar to ArrayList, but with two differences:
Vector proves to be very useful if you don't know the size of the array in advance, or you just need one that can change sizes over the lifetime of a program.
The Vector class supports four constructors. The first form creates a default vector, which has an initial size of 10:
The third form creates a vector whose initial capacity is specified by size and whose increment is specified by incr. The increment specifies the number of elements to allocate each time that a vector is resized upward:
Apart from the methods inherited from its parent classes, Vector defines following methods:
SN | Methods with Description |
1 | void add(int index, Object element) Inserts the specified element at the specified position in this Vector. |
2 | boolean add(Object o) Appends the specified element to the end of this Vector. |
3 | boolean addAll(Collection 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. |
4 | boolean addAll(int index, Collection c) Inserts all of the elements in in the specified Collection into this Vector at the specified position. |
5 | void addElement(Object obj) Adds the specified component to the end of this vector, increasing its size by one. |
6 | int capacity() Returns the current capacity of this vector. |
7 | void clear() Removes all of the elements from this Vector. |
8 | Object clone() Returns a clone of this vector. |
9 | boolean contains(Object elem) Tests if the specified object is a component in this vector. |
10 | boolean containsAll(Collection c) Returns true if this Vector contains all of the elements in the specified Collection. |
11 | void copyInto(Object[] anArray) Copies the components of this vector into the specified array. |
12 | Object elementAt(int index) Returns the component at the specified index. |
13 | Enumeration elements() Returns an enumeration of the components of this vector. |
14 | 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. |
15 | boolean equals(Object o) Compares the specified Object with this Vector for equality. |
16 | Object firstElement() Returns the first component (the item at index 0) of this vector. |
17 | Object get(int index) Returns the element at the specified position in this Vector. |
18 | int hashCode() Returns the hash code value for this Vector. |
19 | int indexOf(Object elem) Searches for the first occurence of the given argument, testing for equality using the equals method. |
20 | int indexOf(Object 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. |
21 | void insertElementAt(Object obj, int index) Inserts the specified object as a component in this vector at the specified index. |
22 | boolean isEmpty() Tests if this vector has no components. |
23 | Object lastElement() Returns the last component of the vector. |
24 | int lastIndexOf(Object elem) Returns the index of the last occurrence of the specified object in this vector. |
25 | int lastIndexOf(Object elem, int index) Searches backwards for the specified object, starting from the specified index, and returns an index to it. |
26 | Object remove(int index) Removes the element at the specified position in this Vector. |
27 | 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. |
28 | boolean removeAll(Collection c) Removes from this Vector all of its elements that are contained in the specified Collection. |
29 | void removeAllElements() Removes all components from this vector and sets its size to zero. |
30 | boolean removeElement(Object obj) Removes the first (lowest-indexed) occurrence of the argument from this vector. |
31 | void removeElementAt(int index) removeElementAt(int index) |
32 | protected void removeRange(int fromIndex, int toIndex) Removes from this List all of the elements whose index is between fromIndex, inclusive and toIndex, exclusive. |
33 | boolean retainAll(Collection c) Retains only the elements in this Vector that are contained in the specified Collection. |
34 | Object set(int index, Object element) Replaces the element at the specified position in this Vector with the specified element. |
35 | void setElementAt(Object obj, int index) Sets the component at the specified index of this vector to be the specified object. |
36 | void setSize(int newSize) Sets the size of this vector. |
37 | int size() Returns the number of components in this vector. |
38 | List subList(int fromIndex, int toIndex) Returns a view of the portion of this List between fromIndex, inclusive, and toIndex, exclusive. |
39 | Object[] toArray() Returns an array containing all of the elements in this Vector in the correct order. |
40 | Object[] toArray(Object[] 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. |
41 | String toString() Returns a string representation of this Vector, containing the String representation of each element. |
42 | void trimToSize() Trims the capacity of this vector to be the vector's current size. |
The following program illustrates several of the methods supported by this collection: