The Vector
class is an implementation of the List interface that allows us to create resizable-arrays similar to the ArrayList class.
Java Vector vs. ArrayList
In Java, both ArrayList
and Vector
implements the List
interface and provides the same functionalities. However, there exist some differences between them.
The Vector
class synchronizes each individual operation. This means whenever we want to perform some operation on vectors, the Vector
class automatically applies a lock to that operation.
It is because when one thread is accessing a vector, and at the same time another thread tries to access it, an exception called ConcurrentModificationException
is generated. Hence, this continuous use of lock for each operation makes vectors less efficient.
However, in array lists, methods are not synchronized. Instead, it uses the Collections.synchronizedList()
method that synchronizes the list as a whole.
Note: It is recommended to use ArrayList
in place of Vector
because vectors less efficient.
Creating a Vector
Here is how we can create vectors in Java.
Vector<Type> vector = new Vector<>();
Here, Type indicates the type of a linked list. For example,
// create Integer type linked list
Vector<Integer> vector= new Vector<>();
// create String type linked list
Vector<String> vector= new Vector<>();
Methods of Vector
The Vector
class also provides the resizable-array implementations of the List
interface (similar to the ArrayList
class). Some of the Vector
methods are:
Add Elements to Vector
add(element)
- adds an element to vectorsadd(index, element)
- adds an element to the specified positionaddAll(vector)
- adds all elements of a vector to another vector
For example,
import java.util.Vector;
class Main {
public static void main(String[] args) {
Vector<String> mammals= new Vector<>();
// Using the add() method
mammals.add("Dog");
mammals.add("Horse");
// Using index number
mammals.add(2, "Cat");
System.out.println("Vector: " + mammals);
// Using addAll()
Vector<String> animals = new Vector<>();
animals.add("Crocodile");
animals.addAll(mammals);
System.out.println("New Vector: " + animals);
}
}
Output
Vector: [Dog, Horse, Cat] New Vector: [Crocodile, Dog, Horse, Cat]
Access Vector Elements
get(index)
- returns an element specified by the indexiterator()
- returns an iterator object to sequentially access vector elements
For example,
import java.util.Iterator;
import java.util.Vector;
class Main {
public static void main(String[] args) {
Vector<String> animals= new Vector<>();
animals.add("Dog");
animals.add("Horse");
animals.add("Cat");
// Using get()
String element = animals.get(2);
System.out.println("Element at index 2: " + element);
// Using iterator()
Iterator<String> iterate = animals.iterator();
System.out.print("Vector: ");
while(iterate.hasNext()) {
System.out.print(iterate.next());
System.out.print(", ");
}
}
}
Output
Element at index 2: Cat Vector: Dog, Horse, Cat,
Remove Vector Elements
remove(index)
- removes an element from specified positionremoveAll()
- removes all the elementsclear()
- removes all elements. It is more efficient thanremoveAll()
For example,
import java.util.Vector;
class Main {
public static void main(String[] args) {
Vector<String> animals= new Vector<>();
animals.add("Dog");
animals.add("Horse");
animals.add("Cat");
System.out.println("Initial Vector: " + animals);
// Using remove()
String element = animals.remove(1);
System.out.println("Removed Element: " + element);
System.out.println("New Vector: " + animals);
// Using clear()
animals.clear();
System.out.println("Vector after clear(): " + animals);
}
}
Output
Initial Vector: [Dog, Horse, Cat] Removed Element: Horse New Vector: [Dog, Cat] Vector after clear(): []
Others Vector Methods
Methods | Descriptions |
---|---|
set() |
changes an element of the vector |
size() |
returns the size of the vector |
toArray() |
converts the vector into an array |
toString() |
converts the vector into a String |
contains() |
searches the vector for specified element and returns a boolean result |