Random seed question...

Newbie & Debugging Questions
#1

The game I’m working on has a random 2d level generator. The subrutine, that creates the level, accepts a (long) argument that if not zero, uses that value as the random seed. I have some numbers (seeds) that create some interesting levels. So when I use the number zero, it doesn’t set the seed, and just leaves the “default” seed alone. I have seen some pretty interesting levels generated this way as well. My question is: Is there a way to get the current seed that the random generator is using (when I have not specifically set one)? I believe if I could get this number then I could virtually use this as the level ID number and allow players to use the same “random” level over and over.

#2

Solution:
After giving it some thought, I came up with a work-around.

Random rndm = new Random();
    	
    	if (seed != 0)
    	{
    		rndm.setSeed(seed);
    	} else {
    		seed = rndm.nextLong();
    		rndm.setSeed(seed);
    	}

If no seed (not zero) is provided, I just randomly randomize the seed. :wink:
The subrutine is now a function that returns the seed, so I can store it in a value, so the players can request the “ID” of the level.

#3

Replace:

seed = rndm.nextLong();

with:

seed = System.currentTimeMillis();

If you want the default behavior.

#4

oNyx’s one is the “default” one used by Random, but Gbeebe’s one is “better”. With the default one, you’re losing 40 years worth of maps! xD

#5

lol =D

btw if you just don’t set a seed, isn’t it default behavior that it uses none/random
not sure about the Random class, might confuse it with some C++ class

#6

Minecraft requires a seed for the world generator. It uses System.currentTimeMillis() if I’m not mistaken.
From http://www.minecraftwiki.net/wiki/Seed_(Level_Generation):

[quote]If you leave the seed field blank, the game will use the time (computer clock) as a seed. Leaving the seed field blank will not produce the same map every time. Using seed 0 in singleplayer will also be ignored, as though it were left blank.
[/quote]

#7

[/quote]
I just thought that if you dont even call .setSeed(seed);, using System.currentTimeMillis() or something similar is the default behavior.

#8 
public Random() {
    this(seedUniquifier() ^ System.nanoTime());
}

public Random(long seed) {
    this.seed = new AtomicLong(initialScramble(seed));
}

It also uses some fancy functions to make the seed “more random”. Doesn’t work that well IMHO. Try feeding it the values 0-100 and generating a random value, and you’ll see what I mean…