# Hash table

Discussion in 'Java' started by ruds, May 25, 2007.

1. ### rudsGuest

hi,
I want to know how can i retrive a key from the given value from a
hash table?
suppose my table conatins:
KEY VALUE
1 3
2 10
3 12
4 15
if i have value 10 how do i get its corresponding key??

ruds, May 25, 2007

2. ### ShaneGuest

ruds wrote:

> hi,
> I want to know how can i retrive a key from the given value from a
> hash table?
> suppose my table conatins:
> KEY VALUE
> 1 3
> 2 10
> 3 12
> 4 15
> if i have value 10 how do i get its corresponding key??

The same way you knew where to insert the other values into your hash?

--
Math problems? Call 1-800-[(10x)(13i)2]-[sin(xy)/2.362x].

Shane, May 25, 2007

3. ### Thomas SchodtGuest

ruds wrote:
> hi,
> I want to know how can I retrive a key from the given value from a
> hash table?

suppose your table contains:
KEY VALUE
1 10
2 10
3 20
4 20
if you have value 10 which is its corresponding key?

Thomas Schodt, May 25, 2007
4. ### Mike SchillingGuest

"ruds" <> wrote in message
news:...
> hi,
> I want to know how can i retrive a key from the given value from a
> hash table?
> suppose my table conatins:
> KEY VALUE
> 1 3
> 2 10
> 3 12
> 4 15
> if i have value 10 how do i get its corresponding key??

You can iterate throught the set of entries (Map.entrySet()), looking for a
match. Or, if the values are unique, you can create a second hash table
that reverses keys and values, and look it up directly.

Mike Schilling, May 25, 2007
5. ### Roedy GreenGuest

Roedy Green, May 25, 2007
6. ### Hendrik MarynsGuest

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Roedy Green schreef:
> On 24 May 2007 23:00:50 -0700, ruds <> wrote, quoted
> or indirectly quoted someone who said :
>
>> hi,
>> I want to know how can i retrive a key from the given value from a
>> hash table?
>> suppose my table conatins:
>> KEY VALUE
>> 1 3
>> 2 10
>> 3 12
>> 4 15
>> if i have value 10 how do i get its corresponding key??

Jakarta Commons Collections defines the BidiMap interface and gives some
implementations.

I can provide you with a generified version if you wish.

H.
- --
Hendrik Maryns
http://tcl.sfs.uni-tuebingen.de/~hendrik/
==================
http://aouw.org
Ask smart questions, get good answers:
http://www.catb.org/~esr/faqs/smart-questions.html
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Hendrik Maryns, May 25, 2007

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