What is the difference between size and capacity of a Vector in Java?

The size of a vector represents the number of components in the vector. The capacity of a vector represents the maximum number of elements the vector can hold.

Example:

import java.util.*; public class VectorDemo {    public static void main(String args[]) {       Vector v = new Vector(3, 2);       System.out.println("Initial size: " + v.size());       System.out.println("Initial capacity: " + v.capacity());       v.addElement(new Integer(1));       v.addElement(new Integer(2));       v.addElement(new Integer(3));       v.addElement(new Integer(4));       System.out.println("Capacity after four additions: " + v.capacity());       v.addElement(new Double(5.45));       System.out.println("Current capacity: " + v.capacity());       v.addElement(new Double(6.08));       v.addElement(new Integer(7));       System.out.println("Current capacity: " + v.capacity());       v.addElement(new Float(9.4));       v.addElement(new Integer(10));       System.out.println("Current capacity: " + v.capacity());       v.addElement(new Integer(11));       v.addElement(new Integer(12));       System.out.println("First element: " + (Integer)v.firstElement());       System.out.println("Last element: " + (Integer)v.lastElement());       if(v.contains(new Integer(3)))       System.out.println("Vector contains 3.");       Enumeration vEnum = v.elements();       System.out.println("\nElements in vector:");       while(vEnum.hasMoreElements())       System.out.print(vEnum.nextElement() + " ");       System.out.println();    } }

Output:

Initial size: 0 Initial capacity: 3 Capacity after four additions: 5 Current capacity: 5 Current capacity: 7 Current capacity: 9 First element: 1 Last element: 12 Vector contains 3. Elements in vector: 1 2 3 4 5.45 6.08 7 9.4 10 11 12