Paul, That was a very good description!
Regards, Rajesh Nair On Wed, Jun 23, 2010 at 2:12 PM, Paul Smith <[email protected]> wrote: > It's all about fast lookup. > > Take any object, how do you look for that object in a container? Go > through the container and check each object one by one until you find > it? Holy O(n) lookup batman! > > Much better would be to sort the objects somehow and at least do > binary search. However, some objects cannot be sorted as they don't > really have an ordering, and some objects are huge so looking them up > is really inefficient that way. > > What you need is some way to quickly convert any object into a > integer, like some kind of identity code, you can then store objects > based on that code, and lookups become much much faster. > > That's the hashcode. > > It doesn't save your complete headache - 2 objects with the same > hashcode aren't necessarily equal, so once you've found all the > objects with the hashcode that you're looking for, you still have to > check the real object for equality - but hash collisions are rare. At > least, with a good hashing algorithm they are ;) > > Paul Smith > > [email protected] > > On Wed, Jun 23, 2010 at 6:07 AM, Rajesh Nair <[email protected]> > wrote: > > Nataraj, > > The hashcode method provides a hash of the object which is primarily used > in > > hash based containers like HashSet and HashMap. > > I do not believe it has anything to do with memory conservation or > creation > > of duplicate objects. > > Regards, > > Rajesh Nair > > > > On Wed, Jun 23, 2010 at 9:24 AM, nataraj subramanian < > [email protected]> > > wrote: > >> > >> So hashcodes are used to prevent creation of duplicate objects? It's a > >> memory conservation thing? > >> > >> On Jun 21, 6:50 pm, Paul Smith <[email protected]> wrote: > >> > Two object which are equal will have equal hashcodes, but two objects > >> > with equal hashcodes aren't necessarily equal. > >> > > >> > Paul Smith > >> > > >> > [email protected] > >> > > >> > On Mon, Jun 21, 2010 at 7:17 AM, Emma Olukha <[email protected] > > > >> > wrote: > >> > > Off the fly..Hash code is an unique id number allocated to an object > >> > > by JVM. > >> > > It basically identifies each object but is not unique. > >> > > >> > > </oluka> > >> > > >> > > On 16 June 2010 14:33, NetBeans <[email protected]> wrote: > >> > > >> > >> wat is mean by hashcode in java > >> > > >> > >> -- > >> > >> You received this message because you are subscribed to the Google > >> > >> Groups > >> > >> "google-codejam" group. > >> > >> To post to this group, send email to [email protected]. > >> > >> To unsubscribe from this group, send email to > >> > >> [email protected]<google-code%[email protected]> > . > >> > >> For more options, visit this group at > >> > >>http://groups.google.com/group/google-code?hl=en. > >> > > >> > > -- > >> > > You received this message because you are subscribed to the Google > >> > > Groups > >> > > "google-codejam" group. > >> > > To post to this group, send email to [email protected]. > >> > > To unsubscribe from this group, send email to > >> > > [email protected]<google-code%[email protected]> > . > >> > > For more options, visit this group at > >> > >http://groups.google.com/group/google-code?hl=en. > >> > >> -- > >> You received this message because you are subscribed to the Google > Groups > >> "google-codejam" group. > >> To post to this group, send email to [email protected]. > >> To unsubscribe from this group, send email to > >> [email protected]<google-code%[email protected]> > . > >> For more options, visit this group at > >> http://groups.google.com/group/google-code?hl=en. > >> > > > > -- > > You received this message because you are subscribed to the Google Groups > > "google-codejam" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > > [email protected]<google-code%[email protected]> > . > > For more options, visit this group at > > http://groups.google.com/group/google-code?hl=en. > > > > -- > You received this message because you are subscribed to the Google Groups > "google-codejam" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]<google-code%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/google-code?hl=en. > > -- You received this message because you are subscribed to the Google Groups "google-codejam" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-code?hl=en.
