Java Vector Class

The Vector class provides "Arrays" of variable sizes. Vector is very much beneficial than Arrays.

Java Vector class

Properties Vector class

  • It is similar to an array, but vector holds multiple datatype objects.
  • Vector do not have any fixed size like arrays. It is having a variable size.
  • Vector grows automatically while inserting new objects in it.
  • Vector provides it's own methods for inserting and deleting elements.
  • Vector automatically resizes while changing it's contents whenever required.

Difference between Vector and Array

Vector have more benefits than Array.

Vector Array
Vector is like a array but holds multiple objects of different datatypes. Array stores only similar data elements.
Vector does not have any fixed size. No need to specify while declaration. Array have fixed size.
Vector increases it's size automatically when the new objects are added. Array never increases from it's fixed size. It results in overflow error.
Vector does not waste the memory space. Array causes more wastage of memory space than vector.
Vector have several methods for performing operations in easier way. Array does not have methods to perform operations like vector.
Vector cannot directly store the values. We need wrapper classes for converting into vector object. Array directly stores the values of same type. Array does not need any classes like vector.
Vector methods are
add(), clear(),get(),size() etc		 Array methods are
toString(),wait(),equals() etc

Vector Syntax

Vector is created like arrays like without specifieng size or with size.

Vector class is stored inside the package java.util.Vector We need to import it before using in the program.

Vector class has three constructors for creation.

Vector vectorName = new Vector();
    
    or 
    
Vector vectorName = new Vector(size); 

    or 
    
Vector vectorName = new Vector(initialCapacity, inCapacityIncrement);

Creating a Vector Example

Following example shows how to create vector 

import java.util.Vector;
class VectorTest 
{
    public static void main(String args[])
    {
	Vector v1 = new Vector();    // empty vector of unknown items
	Vector v2 = new Vector(15);    // initial size of 15
	Vector v3 = new Vector(10,1);    // grows by 1
    }
}

Methods of Vector class

Vector provides serveral methods for performing operations very quickly.

Assume vector is declared as Vector v = new Vector();

Method Name Description
v.add(object) This method adds an object to the Vector v.
v.addElement(element) This method adds a new element at the end of list.
v.size() This method gives the size of the Vector object.(total inserted elements)
v.removeElement(element) This method removes the specified element from the vector.
v.removeElementAt(index) This method removes the specified element from given index.
v.removeAllElementAt() This method removes all the present elements from the vector.
v.insertElementAt(element, index) This method inserts the new element at specified index.
v.elementAt(index) This method gets the element from given index.
v.clear() This method removes all the elements from vector object.
v.contains(object) This method returns boolean true if given object is present in the vector.
v.lastElement() This method gets the last element from the vector.
v.remove(index) This method removes the element from given index. It also shifts all elements to down.
v.set(index,newElement) This method replaces given index element with new index element.

Example - Insert,Delete and Display the Elements of Vector using above methods.

import java.util.Vector;
class VectorOperations 
{
    Vector v = new Vector();
    void insert()
    {
	v.addElement(new Integer(20));
	v.addElement(new Float(3.14f));
	v.addElement(new Double(9.818283));
	v.addElement(new String("AndroidBerry.com"));
    }
    void delete()
    {
	v.removeElementAt(2);
    }
    void display()
    {
	for(int i=0;i<v.size();i++)
	   System.out.println("vector of "+i+" = "+v.elementAt(i));
    }
    public static void main(String args[])
    {
	VectorOperations n = new VectorOperations();
	n.insert();
	n.display();
	System.out.println("\nAfter deleting 2nd element\n");
	n.delete();
	n.display();
    }
}

Output

vector of 0 = 20
vector of 1 = 3.14
vector of 2 = 9.818283
vector of 3 = AndroidBerry.com

After deleting 2nd element

vector of 0 = 20
vector of 1 = 3.14
vector of 2 = AndroidBerry.com
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