Java – Vector class with example

September 3, 2016 SJ Collection 0

In this article, we will discuss Vector class – one of the List implemented class in detail

1. Key points about Vector:

  • Vector is a legacy class
  • introduced in Java 1.0 version
  • all its method are synchronized i.e.; thread-safe for any operation

2. Vector:

  • Vector is implementation class of List interface (i.e.; Vector implements List)
  • Vector uses resizable array or grow-able array to store element/objects
  • Duplicate element/objects are allowed to be inserted
  • Insertion order is maintained
  • Allows NULL insertion (no limit, any number of NULL insertion is allowed)
  • Without generics, Vector allows to insert any type of objects;
  • with generics, it is type-bounded (except, if we take Object as type within angle brackets)
  • Elements retrieval is faster as Vector works on zero-based index
  • Manipulation (i.e.; addition/deletion of element from middle of Vector) is very slow, as it requires lot of shifting work internally
  • Note: this is exactly same as that of ArrayList except all methods of Vector class is synchronized. Hence, it is thread-safe
  • Present in java.util package and extends java.util.AbstractList implements java.util.List interface
  • Also, implements java.util.RandomAccess, java.lang.Cloneable, java.io.Serializable marker interfaces which provides special ability to Vector (provided by JVM at run time) like
  • java.util.Random Access: to access any random element/objects with same speed
  • java.lang.Cloneable: to create a duplicate object or to clone an object
  • java.io.Serializable: to transfer objects across network
7-Vector-in-java

Source: Team BenchResources.Net

3. Vector constructors:

3.1 Vector v = new Vector();

  • creates an empty Vector object of size 10
  • when maximum size of the Vector is reached, then new Vector of bigger size is created using below formula
    Capacity = New Vector size = 2 * current size (double in size)
  • old Vector item values will be copied into new Vector

3.2 Vector v = new Vector(int initialCapacity);

  • creates an empty Vector object of specified size (or initial capacity)
  • when maximum size is reached, above formula will be applied and new ArryaList will be created

3.3 Vector v = new Vector(int initialCapacity, int incrementalCapacity);

  • creates an empty Vector object of specified size (or initial capacity)
  • when maximum size is reached, new vector is created with a size of (old vector size + increment capacity value)

3.4 Vector v = new Vector(Collection c);

  • creates an equivalent Vector object for the specified collection
  • it is basically used for inter-conversion between collection objects

4. Vector methods:

  • Vector specific methods from Java 1.0 version
Vector method Description
void addElement(Object obj);add/inserts specified element/object at the end of the invoking vector
boolean removeElement(Object obj);removes first occurrence of specified element/object from the invoking vector
void removeElementAt(int index);removes element/object from the invoking vector at the specified index
void removeAllElements();removes all element/objects from the invoking vector

 

after removing all element/objects, size of vector will become zero

Object elementAt(int index);returns element/object from the invoking vector at the specified index
Object firstElement();returns first element/object from the invoking vector
Object lastElement();returns last element/object from the invoking vector
int size();returns number of elements present in the invoking vector (at the time of invoking)
 int capacity();returns current capacity of the invoking vector
Enumeration elements();returns Enumeration of the elements in the invoking vector

5. Vector examples:

VectorAddAndRemove.java

package in.bench.resources.java.collection;

import java.util.Vector;

public class VectorAddAndRemove {

	public static void main(String[] args) {

		// creating Vector object of type String
		Vector<String> vec = new Vector<String>();

		// adding elements to Vector object
		vec.addElement("Sundar Pichai");
		vec.addElement("Satya Nadella");
		vec.addElement("Shiv Nadar");
		vec.addElement("Shantanu Narayen");
		vec.addElement("Sundar Pichai");
		vec.addElement("Francisco D’Souza");

		System.out.println("Iterating Vector values\n");

		// Iterating using enhanced for-loop
		for(String str : vec){
			System.out.println(str);
		}

		// removing element at 4th index
		vec.removeElement(4);

		// to print all values of Vector
		System.out.println("\n\nVector values after removal "
				+ "at 4th index postion \n" + vec);
	}
}

Output:

Iterating Vector values

Sundar Pichai
Satya Nadella
Shiv Nadar
Shantanu Narayen
Sundar Pichai
Francisco D’Souza

Vector values after removal at 4th index postion 

[Sundar Pichai, Satya Nadella, Shiv Nadar,
Shantanu Narayen, Francisco D’Souza]

Note: All methods of Vector are synchronized hence it is thread-safe

Related Articles:

References:

Happy Coding !!
Happy Learning !!

Java - ArrayList v/s Vector
Java - LinkedList class with example

Related posts:

  1. Java – ArrayList v/s Vector
  2. Java – Stack class
  3. Java – Enumeration interface with example
  4. Java – Iterate through Vector in 5 ways