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Java - how to generate Random numbers in while loop

Kyle Hamilton
on
I want to generate two random numbers, then check for a condition, and as long as condition holds true, generate two new different random numbers.

This is what I have... and I suspect it's probably wrong...

Random hit = new Random();
				int rowRan = hit.nextInt(9);
				int colRan = hit.nextInt(9);
				
				while(ships[rowRan][colRan] == '-'  || ships[rowRan][colRan] == '*'){
					Random nexthit = new Random();
					rowRan = nexthit.nextInt(9);
					colRan = nexthit.nextInt(9);
				}
				rowInt = rowRan;
				colInt = colRan;

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Awarded 2011
Awarded 2011

Commented:
you can do that, i believe, but you actually don't need to craete new Rndom every time:
Random hit = new Random();
				int rowRan = hit.nextInt(9);
				int colRan = hit.nextInt(9);
				
				while(ships[rowRan][colRan] == '-'  || ships[rowRan][colRan] == '*'){
					
					rowRan = hit.nextInt(9);
					colRan = hit.nextInt(9);
				}
				rowInt = rowRan;
				colInt = colRan;
                                  

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Awarded 2011
Awarded 2011

Commented:
Random hit = new Random();

creates new random value using the cvurren millisecond as a seed,
after that each hit.nextInt(9) will generate a random int less than 9
you do not need to recreate the Random object every time - it will generate different random int less than 9 eech time ytou call it, so you don;t need ti recreate it every time
Awarded 2011
Awarded 2011
Commented:
As it will be useing the current time as a seed every time and current time will be changing so, igf you would be creating the new Random every time it will have diofferent seed and will generate bew sequence, so probably it should not maytter in thuis case, but anyway you don't need to create new Random object every time
You create it once and then generate the random integers as much as you want
Kyle HamiltonData Scientist
Most Valuable Expert 2014

Author

Commented:
I was hoping for that.

So when is a Random generated with the same "seed" giving you the same random number?

(not sure what I'm talking about... it's something I read..)
Awarded 2011
Awarded 2011

Commented:
yes,
if you say

Random r = new Random(25345123);

and then you say

int i = r.next(100);
let's assume each time you'll be getting as i say

41, 13, 12, 56...


then somehwre down the roda you again create the Random with the same seed


r = new Random(25345123);

and again do

i = r.nextInt(100);

several tiumes, then you'are guranteed that you'll be getting the same sequence:

41, 13, 12, 56...

That is waht mesans seed. If you use different seemd then sequence will be different

But within each sequence numbers are still coming in random way
So you don't need to create Random object again
Kyle HamiltonData Scientist
Most Valuable Expert 2014

Author

Commented:
cool. That's exactly what I wanted to know....

Thanks.