VECTORS- Ankita R Karia

Vectors Vector implements a DYNAMIC ARRAY.

Vectors can hold objects of any type and any number.

Vector class is contained in java.util package

Vector is different from ARRAY in two ways:-

1. Vector is synchronized.

2. It contains many legacy methods that are not part of the

collection framework. 1. Enumeration.2. Iterator

Declaring VECTORS

Vector list = new Vector();

Vector list = new Vector(int size);

Vector list = new Vector(int size, int incr);

Creates a default vector, which has an initial size 10.

Creates a vector, whose initial capacity is specified by size.

Creates a vector, whose initial capacity is specified by size and whose increment is specified by incr.

Vectors (Contd….)

A vector can be declared without specifying any size explicitly.

A vector without size can accommodate an unknown number of

items.

Even when size is specified, this can be overlooked and a different

number of items may be put into the vector

In contrast, An ARRAY must be always have its size specified.

WRAPPER CLASSES

Vectors cannot handle primitive data types like int, float, long, char and double.

Primitive data types may be converted into objects using the WRAPPER classes contained in java.lang package.

SIMPLE TYPE WRAPPER CLASSES

boolean Boolean

char Character

double Double

float Float

int Integer

long Long

Converting Primitive data types

to Objects.SYNTAX ACTION

Integer ob=new Integer(i) Converts primitive integer to Integer object

Float ob=new Float(f) Converts primitive float to float object

Converting Objects to Primitive data types.

SYNTAX ACTION

int i=ob.intValue() Converts Integer object to primitive integer

float f=ob.floatValue() Converts Float object to primitive float

Converting Numbers to Strings

Using toString() methodSYNTAX ACTION

str=Integer.toString(i) Converts primitive integer to string

str=Float.toString(f) Converts primitive float to string

There are other wrapper classes methods Refer Balagurusamy

VECTOR METHODSvoid addElement(Object element) The object specified by element is

added to the vector

int capacity() Returns the capacity of the vector

boolean contains(Object element) Returns true if element is contained by the vector, else false

void copyInto(Object array[]) The elements contained in the invoking vector are copied into the array specified by array[]

elementAt(int index) Returns the element at the location specified by index

Object firstElement(). Returns the first element in the vector

VECTOR METHODSvoid insertElementAt(Object element, int index)

Adds element to the vector at the location specified by index

boolean isEmpty() Returns true if Vector is empty, else false

Object lastElement() Returns the last element in the vector

void removeAllElements() Empties the vector. After this method executes, the size of vector is zero.

void removeElementAt(int index) Removes element at the location specified by index

void setElementAt(Object element, int index)

The location specified by index is assigned element

VECTOR METHODSvoid setSize(int size) Sets the number of elements in the

vector to size. If the new size is less than the old size, elements are lost. If the new size is larger than the old, null elements are added

int size() Returns the number of elements currently in the vector

ENUMERATION INTERFACE

Defines the methods by which you can enumerate the elements in a collection of objects

OBTAIN ONE AT TIME

boolean hasMoreElements() Object nextElement()

Returns true while there are still more elements to extract

and false otherwise

Returns the next object in enumeration

PROGRAMMING EXAMPLE

Write a program that accepts a shopping list of five items from the command line and stores them in a vector.

Modify the program to accomplish the following:-

1. To delete an item in the list.2. To add an item at a specified position in

the list.3. To add an item at the end of the list.4. To print the contents of the vector.