Vector class in java

Vector Class in Java

Vector class implements List interface so vector class is also growable in nature which internally resizes array when the elements gets added or removed.

Vector class is synchronized in nature that’s why whatever operations we perform on vectors. Vector class automatically applies a lock to that operation.

Features of Vector class

Remaining features are similar to ArrayList class except

1] Vector class is thread safe or you can say it is synchronized in nature.

2] Since JDK 1.0 Vector class is present in java so it will contains many legacy feature available like Vector class used Enumeration interface methods.

Vector class Declaration

public class Vector

    extends AbstractList

    implements List, RandomAccess, Cloneable, java.io.Serializable

Ways to create vector class object / Initial capacity of vector class

Note:  By default vector double its size.

1] Default Vector class capacity

Vector vector = new Vector();

public Vector() {

        this(10);

}

It creates an empty Vector with the default initial capacity of 10. It means the Vector will be re-sized when the 11th elements needs to be inserted into the Vector. And it will resize its capacity to 20.

2] Constructs an empty vector with the specified initial capacity

We can create vector class object by providing initialCapacity.

Vector vector = new Vector(4);

public Vector(int initialCapacity) {

        this(initialCapacity, 0);

}

When we add 5th element in vector class object then it will automatically resize its capacity to double of original Example: It will create 8 as new capacity.

3] Constructs an empty vector with the specified initial capacity and capacity increment.

Vector vector = new Vector<>(initialCapacity, capacityIncrement)

public Vector(int initialCapacity, int capacityIncrement) {

        super();

        if (initialCapacity < 0)

            throw new IllegalArgumentException("Illegal Capacity: "+

                                               initialCapacity);

        this.elementData = new Object[initialCapacity];

        this.capacityIncrement = capacityIncrement;

    }

initialCapacity - the initial capacity of the vector

capacityIncrement - the amount by which the capacity is increased when the vector overflows

Vector class Example

package com.vr.techfloaters;

import java.util.Vector;

public class VectorExample {

     public static void main(String[] args) {

          

          

           /* Vector of default capacity(size) of 10 */

           Vector v1 = new Vector<>();

          

           /* Vector of initial capacity(size) of 3 and capacityIncrement is 5*/

           Vector v2 = new Vector<>(3, 5);

          

           /* Vector of initial capacity(size) of 4 */

           Vector vector = new Vector<>(4);

                    

           /* Adding elements to a vector*/

           vector.add(101);

           vector.add("java");

           vector.add(null);

           vector.add(null);

           vector.add(102);

           vector.add(103);

           vector.add(103);

          

           /* check size and capacityIncrement*/

           System.out.println(vector);

           System.out.println("Size is: "+vector.size());

         System.out.println("Default capacity increment is: "+vector.capacity());

          

         System.out.println("--------------------------");

        

         vector.addElement(201);

         vector.addElement("ashok");

          

         System.out.println(vector);

           System.out.println("Size after addElement is: "+vector.size());

         System.out.println("Default capacity  after addElement is: "+vector.capacity());

     }

}   

Output

[101, java, null, null, 102, 103, 103]

Size is: 7

Default capacity increment is: 8

--------------------------

[101, java, null, null, 102, 103, 103, 201, ashok]

Size after addElement is: 9

Default capacity  after addElement is: 16