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Help needed to generate a unique random number without importing any third party jar's.

 
Greenhorn
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Hi All,
I want to generate unique random number from(0 to n number) such that if i run the program everytime it should give me a unique random number all the time.numbers should not repeated at any cost.

Please help me...

Thanks in Advance..
 
Ranch Hand
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You can do it by using Math.random method. You have to maintain a list of all the numbers you have generated and used. Before returning the random number you have to check that it is already present in the list or not? If it is in list then you have to generate the function again.

HTH
 
Bartender
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A Set would be more suitable instead of a list.
 
Marshal
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I think you are supposed to call this random sampling from a declining population, or something similar. Please do a search of this forum; similar questions are asked about 6-10 times a year, and there will probably be helpful suggestions in the old threads.
 
Master Rancher
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Maneesh Godbole wrote:A Set would be more suitable instead of a list.


For what HG suggested, yes. However there's another algorithm using a List and Collections.shuffle(); this works quite well as long as N is not too large.
 
Amith Bhavikatti
Greenhorn
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Thanks Guys for your answers.

I Hope it works.
 
lowercase baba
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you also need to thnk about what you will do when your program is run the (n+1)th time.
 
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