Java Source Codes

random number generator

package corejava;

/**
An improved random number generator
Gives a set of random integers that does not exhibit
as much correlation as the method used by the Java random number generator.

*/

public class RandomIntGenerator
{ /**
Constructs an object that generates random integers in a given range
@param l the lowest integer in the range
@param h the highest integer in the range
*/

public RandomIntGenerator(int l, int h)
{ low = l;
high = h;
}

/**
Generates a random integer in a range of integers
@return a random integer
*/

public int draw()
{ int r = low
+ (int)((high - low + 1) * nextRandom());
return r;
}

/**
test stub for the class
*/

public static void main(String[] args)
{ RandomIntGenerator r1
= new RandomIntGenerator(1, 10);
RandomIntGenerator r2
= new RandomIntGenerator(0, 1);
int i;
for (i = 1; i <= 100; i++)
System.out.println(r1.draw() + " " + r2.draw());
}

private static double nextRandom()
{ int pos =
(int)(java.lang.Math.random() * BUFFER_SIZE);
if (pos == BUFFER_SIZE) pos = BUFFER_SIZE - 1;
double r = buffer[pos];
buffer[pos] = java.lang.Math.random();
return r;
}

private static final int BUFFER_SIZE = 101;
private static double[] buffer
= new double[BUFFER_SIZE];
static
{ int i;
for (i = 0; i < BUFFER_SIZE; i++)
buffer[i] = java.lang.Math.random();
}

private int low;
private int high;
}

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