Vectors

[Ragu Sivaraman]

Ranchers :
Vector v = new Vector(1);
for(int i = 0; i<20; i++)
v.add(new Integer(i));
System.out.println(v.size());
System.out.println(v.capacity());
Ans: 20
32
How come the capacity is 32 , when the increment is 0??
If i do Vector v = new Vector(1,1), its works fine
Q2: Whats the critical difference between add() and addElement()

Ragu

[Michael Ernest]

Here's how you understand this kinda behavior:

import java.io.PrintStream;
import java.util.Vector;
public class VecCheck
{
   public static void main(String arg[]) {
      PrintStream out = System.out;
      Vector vec = new Vector(1);
      out.println("size: " + v.size());
      out.println("cap : " + v.capacity());
      for (int i = 0; i < 20; i++) {
         vec.add(new Integer(i));
         out.println("i   : " + i);
         out.println("size: " + v.size());
         out.println("cap : " + v.capacity() + "\n");
      }
      out.println("size: " + v.size());
      out.println("cap : " + v.capacity());
   }

Now, you tell us what's going on.
------------------
Michael Ernest, co-author of: The Complete Java 2 Certification Study Guide

[Sasikanth Malladi]

That's one of the best replies I've seen!! I've heard that a wise man answers a question with another question and now I'm seeing it in action!
Sasikanth

[Marilyn de Queiroz]

Q2: Whats the critical difference between add() and addElement()

addElement:

"This method is identical in functionality to the add(Object) method (which is part of the List interface)."

Reference

[This message has been edited by Marilyn deQueiroz (edited October 16, 2001).]

[Ragu Sivaraman]

Originally posted by Michael Ernest:
[B]Here's how you understand this kinda behavior:

import java.io.PrintStream;
import java.util.Vector;
public class VecCheck
{
   public static void main(String arg[]) {
      PrintStream out = System.out;
      Vector vec = new Vector(1);
      out.println("size: " + v.size());
      out.println("cap : " + v.capacity());
      for (int i = 0; i < 20; i++) {
         vec.add(new Integer(i));
         out.println("i   : " + i);
         out.println("size: " + v.size());
         out.println("cap : " + v.capacity() + "\n");
      }
      out.println("size: " + v.size());
      out.println("cap : " + v.capacity());
   }

Now, you tell us what's going on.
[/B]

Mike
Thankyou very much for response
You do make sure that we understand thoroughly
I appreciate that very much
From this code what i understood was
Whenever the size=capacity,
the vectors doubles its capacity

Please correct me if i am wrong
thankx
Ragu
PS: Why there is a special method addElement(Obj) for Vector?
It seems to do the same work as add(Obj) from list?

[Michael Ernest]

You are of course right, Ragu. As an bonus question: how do you change the behavior so capacity doesn't double every time the Vector fills up?
Marilyn's comments on add() and addElement() are correct: add() satisfies the List interface requirement, so that Vector can implement List. There's no need for them to be different, but if you took out addElement() because it's redundant, you might break someone's code. That's what happens when you need to redesign your interface...
------------------
Michael Ernest, co-author of: The Complete Java 2 Certification Study Guide

[Muhammad Farooq]

use another constructor to create Vector object as:
Vector(int initialCapacity, int capacityIncrement)
Constructs an empty vector with the specified initial capacity and capacity increment.
Vector v = new Vector(1, 10);
it will icrease the vector capacity in increment of 10.
--Farooq