/*
* @(#)$Id$
*
* Copyright 2006-2008 Makoto YUI
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Contributors:
* Makoto YUI - initial implementation
*/
package xbird.util.distribution;
import java.util.Random;
/**
*
* <DIV lang="en"></DIV>
* <DIV lang="ja"></DIV>
*
* @author Makoto YUI (yuin405+xbird@gmail.com)
* @link http://en.wikipedia.org/wiki/Zipf%27s_law
*/
public final class ZipfGenerator {
private final Random random;
private final double skew_d;
public ZipfGenerator() {
this(2d);
}
public ZipfGenerator(double skew) {
if(skew <= 1d) {
throw new IllegalArgumentException("skew should be greater than 1.0f");
}
this.random = new Random();
this.skew_d = skew;
}
public double nextDouble() {
double p = random.nextDouble();
return Math.pow(1d - p, 1d - (1d - skew_d));
}
public long nextLong() {
return Double.doubleToLongBits(nextDouble());
}
}