|
/*
* Copyright (c) 2000 David Flanagan. All rights reserved.
* This code is from the book Java Examples in a Nutshell, 2nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book (recommended),
* visit http://www.davidflanagan.com/javaexamples2.
*/
/**
* This class defines methods for computing pseudo-random numbers, and defines
* the state variable that needs to be maintained for use by those methods.
*/
public class Randomizer {
// Carefully chosen constants from the book "Numerical Recipes in C".
// All "static final" fields are constants.
static final int m = 233280;
static final int a = 9301;
static final int c = 49297;
// The state variable maintained by each Randomizer instance
int seed = 1;
/**
* The constructor for the Randomizer() class. It must be passed some
* arbitrary initial value or "seed" for its pseudo-randomness.
*/
public Randomizer(int seed) {
this.seed = seed;
}
/**
* This method computes a pseudo-random number between 0 and 1 using a very
* simple algorithm. Math.random() and java.util.Random are actually a lot
* better at computing randomness.
*/
public float randomFloat() {
seed = (seed * a + c) % m;
return (float) Math.abs((float) seed / (float) m);
}
/**
* This method computes a pseudo-random integer between 0 and specified
* maximum. It uses randomFloat() above.
*/
public int randomInt(int max) {
return Math.round(max * randomFloat());
}
/**
* This nested class is a simple test program: it prints 10 random ints.
* Note how the Randomizer object is seeded using the current time.
*/
public static void main(String[] args) {
Randomizer r = new Randomizer((int) new java.util.Date().getTime());
for (int i = 0; i < 10; i++)
System.out.println(r.randomInt(100));
}
}
|