vector class

[Ranjeet Kr Rai]

In Vector class how capacity() is different than size() and what about

Vector(int initCapacity, int capIncrement )

[Stephan van Hulst]

The size of a vector is how many items are currently held by it. The capacity is how many items it can hold in total, before it needs more memory.

[Anooj Narvekar]

Ya.. and

Vector(int initCapacity, int capIncrement )

is to initialize vector with a initial capacity, and capIncrement parameter mentions by how much should the current capacity be increased upon filling the vector.

Think of vector as an Array. Instead of increasing the size of vector at every insert into the vector, providing init capacity makes lot of sense as you will avoid un-necessary array copying and re-inserting

[Campbell Ritchie]

Why are you using Vector in the first place, rather than ArrayList?
A lot of people think it was a mistake to permit users to set a size increment like that. So ArrayList doesn't have such a constructor.

[Sunny Bhandari]

You can also read about this in more detail for java source code for that constructor...