Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */ package org.apache.commons.rng.sampling.distribution; import org.apache.commons.rng.UniformRandomProvider; /** * Discrete uniform distribution sampler. */ public class DiscreteUniformSampler extends SamplerBase implements DiscreteSampler { /** Lower bound. */ private final int lower; /** Upper bound. */ private final int upper; /** * @param rng Generator of uniformly distributed random numbers. * @param lower Lower bound (inclusive) of the distribution. * @param upper Upper bound (inclusive) of the distribution. * @throws IllegalArgumentException if {@code lower > upper}. */ public DiscreteUniformSampler(UniformRandomProvider rng, int lower, int upper) { super(rng); if (lower > upper) { throw new IllegalArgumentException(lower + " > " + upper); } this.lower = lower; this.upper = upper; } /** {@inheritDoc} */ @Override public int sample() { final int max = (upper - lower) + 1; if (max <= 0) { // The range is too wide to fit in a positive int (larger // than 2^31); as it covers more than half the integer range, // we use a simple rejection method. while (true) { final int r = nextInt(); if (r >= lower && r <= upper) { return r; } } } else { // We can shift the range and directly generate a positive int. return lower + nextInt(max); } } /** {@inheritDoc} */ @Override public String toString() { return "Uniform deviate [" + super.toString() + "]"; } }