Vector in Java
Introduction
Vectors in
Java uses data in a linear fashion like Array. But it implements a dynamic array
that can grow or shrink as and when required to accommodate adding and removing
data item. In the Java 2 SDK, the Vector class has been included in the
Collection framework to implement the List interface and it comes under the
java.util package. The Vector class is favored over the ArrayList class when we
are creating a multi-threaded application.
- The Vector class is similar to ArrayList class but Vector is synchronized(the main facet of Vector class is that it is thread-safety. ).
- The Vector class is created dynamic Array which can grow and shrink.
- Vector class is a child class of AbstractList class and implements on List interface
- Duplicate element/objects are allowed in Vector
- Insertion order is maintained
- It allows NULL insertion
- Vectors don’t support primitives data types like short, int, double, char, etc.
Advantages of Vector in Java
- Due to its Dynamic size, memory wastage is not happening.
- Vector class is synchronized and it helps in the multithreaded program and helps to check data corruption.
- Vectors have some legacy methods which can be implemented only on vector class and not on the ArrayLists class.
Note: The Vector class may reduce
the performance of the developed application as it is thread safety and it only
allowed one thread as it locked the thread and the remaining thread have to wait
until a thread released the object lock. So it is recommended that if we do not
need thread safety, then we should use the ArrayList class instead of Vector
class.
The Vector class defines the following constructors
public Vector() This a constructor creates an empty vector and its initial data array size is 10
public Vector(int n) This A constructor creates an empty vector with specified size n.
Vector (int initSize, int
incrSize) This form of constructor creates an empty vector with its initial
and increment capacity.
Vector (Collection c) This a constructor creates a vector containing the elements of the specified
collection c.
Apart from the above constructor's Vector define three protected data member
which are as follows
protected int capacity increment
This data member of the vector is
automatically incremented when its size becomes greater than its capacity.
protected int elementCount
The number of valid elements in
the vector.
protected int elementData[]
The array holds the elements of
the vector.
Exmpale
import java.util.*;
public class
TheVectorClassExample
{
public static void main(String args[])
{
Vector<String> student = new
Vector<String>(4);
//Adding elements to a student Vector
student.add("Zainab");
student.add("Sachin");
student.add("Junaid");
student.add("Salim");
student.add("Ashis");
student.add("Deva");
student.add("Danny");
//Checking the size and capacity of
Vector
System.out.println("The Size of
Vector is: "+student.size());
System.out.println("Default
capacity is: "+student.capacity());
//Display Vector elements
System.out.println("Vector element
is: "+student);
student.addElement("Rat");
student.addElement("Cat");
student.addElement("Deer");
//Again check size and capacity after
two insertions
System.out.println("Size after
addition: "+student.size());
System.out.println("Capacity after
addition is: "+student.capacity());
//Display Vector elements again
System.out.println("Elements are:
"+student);
//Checking if Tiger is present or not
in this student or
if(student.contains("Tiger"))
{
System.out.println("Tiger is
present at the index " +student.indexOf("Tiger"));
}
else
{
System.out.println("Tiger is
not present in the list.");
}
//Get the first element
System.out.println("The first
animal of the studenttor is = "+student.firstElement());
//Get the last element
System.out.println("The last
animal of the studenttor is = "+student.lastElement());
// Using Enumeration
Enumeration en = student.elements();
System.out.println("\nStudent
are:");
while(en.hasMoreElements())
System.out.print(en.nextElement() +
" ");
}
}
How to copy a Vector into an Array?
import java.util.*;
public class Vector2JavaArray
{
public static void main(String[] args) {
// Vector class object
Vector<String> vector = new Vector<String>();
vector.add("Aman");
vector.add("Bimal");
vector.add("Jamil");
vector.add("Sachin");
vector.add("Vikas");
System.out.println("Actual vector elements:" + vector);
// Create an Array
String[] copyArray = new String[vector.size()];
// Here we use copyInto Method to copy
vector.copyInto(copyArray);
System.out.println("Copied Array as OUTPUT:");
for (String name : copyArray)
{
System.out.println(name);
}
}
}
Sample output
Actual vector elements:[Aman, Bimal, Jamil, Sachin, Vikas]
Copied Array as OUTPUT:
Aman
Bimal
Jamil
Sachin
Vikas
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