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Vector is a legacy class through which we can construct a dynamic array. As legacy classes came out before the advent collection classes, so unlike collection classes, earlier version of Vector class did not provide iteration over its element in a for-each loop and we could neither get an Iterator to iterate over its elements.

But with the release of Collection Framework and JDK5, Vector class was updated to implement List and Iterable interface, so that it's possible to iterate over its elements in a for-each loop.

Note

Vector class is similar to ArrayList in a way that Vector class is also used to store a collection of object, be it built-in objects or user-defined objects but with a difference.

Difference between ArrayList and Vector Class.

• ArrayList isn't synchronized and hence it is not thread-safe by default on the other hand, Vector class is synchronized and thread-safe.
• As Vector class is a legacy class, hence most of its methods are legacy methods that aren't not entirely part of the Collection Framework.
• ArrayList is a collection class, which is a new modified version of Vector, which is a legacy class.

A simple constructor of Vector class

Vector()
This constructor creates an empty Vector to hold a particular type of objects. Example -

Vector <Integer> v = new Vector <Integer>();

This constructor creates a Vector to hold Integer objects.

Some legacy methods in Vector class.

Methods	Description
int size()	Returns the total number of elements in Vector.
boolean isEmpty()	Returns true if Vector is empty.
E firstElement()	Returns the first element in Vector.
E lastElement()	Returns the last element in Vector.
E elementAt(int index)	Returns the element present in Vector at a specified index.
void addElement(E element)	Inserts an element in the Vector.
boolean contains(Object object)	Returns true if the specified object is present in Vector.
boolean removeElementAt(int index)	Returns true if element present in Vector is removed.

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Vector class example

In this program we have created a Vector to hold String objects and we will add/remove and search elements from this Vector using its methods. Let's see the code now -:

import java.util.*;

class Vector1
{
public static void main(String... ar)
{
Vector<String> vec= new Vector<String>();

vec.addElement("B");
vec.addElement("A");
vec.addElement("T");
vec.addElement("M");
vec.addElement("A");
vec.addElement("N");

System.out.println("Vector = "+vec);

System.out.println("Size of Vector = "+ vec.size());

System.out.println("First element in Vector = "+vec.firstElement());
System.out.println("Last element in Vector = "+vec.lastElement());

System.out.println("Element at 2nd index = "+ vec.elementAt(2));

vec.removeElementAt(2);

System.out.println("After removing element at 2nd index, Vector = "+ vec);

}
}

Output is :

Vector = [B, A, T, M, A, N]
Size of Vector = 6
First element in Vector = B
Last element in Vector = N
Element at 2nd index = T
After removing element at 2nd index, Vector = [B, A, M, A, N]

Program Analysis

• Method addElement() is called to add String objects to the Vector and after populating Vector with String objects, Vector's contents are displayed.
• Method size() is called to display the total number of elements in Vector.
• Method firstElement() is called, which returns the first element in the
• Method lastElement() is called, which returns the last element in the Vector.
• Method elementAt() is called to get element at the 2nd index from Vector and T is returned.
• Method removeElementAt() is called to remove elemnt at 2nd index, hence T is removed.
• After removal of String object T, updated contents of Vector are displayed in the end.

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