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Diffstat (limited to 'src/main/java/org/apache/commons/math/random/RandomData.java')
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diff --git a/src/main/java/org/apache/commons/math/random/RandomData.java b/src/main/java/org/apache/commons/math/random/RandomData.java new file mode 100644 index 0000000..0fc5136 --- /dev/null +++ b/src/main/java/org/apache/commons/math/random/RandomData.java @@ -0,0 +1,272 @@ +/* + * 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.math.random; +import java.util.Collection; + +/** + * Random data generation utilities. + * @version $Revision: 780975 $ $Date: 2009-06-02 11:05:37 +0200 (mar. 02 juin 2009) $ + */ +public interface RandomData { + /** + * Generates a random string of hex characters of length + * <code>len</code>. + * <p> + * The generated string will be random, but not cryptographically + * secure. To generate cryptographically secure strings, use + * <code>nextSecureHexString</code></p> + * <p> + * <strong>Preconditions</strong>:<ul> + * <li><code>len > 0</code> (otherwise an IllegalArgumentException + * is thrown.)</li> + * </ul></p> + * + * @param len the length of the string to be generated + * @return random string of hex characters of length <code>len</code> + */ + String nextHexString(int len); + + /** + * Generates a uniformly distributed random integer between + * <code>lower</code> and <code>upper</code> (endpoints included). + * <p> + * The generated integer will be random, but not cryptographically secure. + * To generate cryptographically secure integer sequences, use + * <code>nextSecureInt</code>.</p> + * <p> + * <strong>Preconditions</strong>:<ul> + * <li><code>lower < upper</code> (otherwise an IllegalArgumentException + * is thrown.)</li> + * </ul></p> + * + * @param lower lower bound for generated integer + * @param upper upper bound for generated integer + * @return a random integer greater than or equal to <code>lower</code> + * and less than or equal to <code>upper</code>. + */ + int nextInt(int lower, int upper); + + /** + * Generates a uniformly distributed random long integer between + * <code>lower</code> and <code>upper</code> (endpoints included). + * <p> + * The generated long integer values will be random, but not + * cryptographically secure. + * To generate cryptographically secure sequences of longs, use + * <code>nextSecureLong</code></p> + * <p> + * <strong>Preconditions</strong>:<ul> + * <li><code>lower < upper</code> (otherwise an IllegalArgumentException + * is thrown.)</li> + * </ul></p> + * + * @param lower lower bound for generated integer + * @param upper upper bound for generated integer + * @return a random integer greater than or equal to <code>lower</code> + * and less than or equal to <code>upper</code>. + */ + long nextLong(long lower, long upper); + + /** + * Generates a random string of hex characters from a secure random + * sequence. + * <p> + * If cryptographic security is not required, + * use <code>nextHexString()</code>.</p> + * <p> + * <strong>Preconditions</strong>:<ul> + * <li><code>len > 0</code> (otherwise an IllegalArgumentException + * is thrown.)</li> + * </ul></p> + * @param len length of return string + * @return the random hex string + */ + String nextSecureHexString(int len); + + /** + * Generates a uniformly distributed random integer between + * <code>lower</code> and <code>upper</code> (endpoints included) + * from a secure random sequence. + * <p> + * Sequences of integers generated using this method will be + * cryptographically secure. If cryptographic security is not required, + * <code>nextInt</code> should be used instead of this method.</p> + * <p> + * <strong>Definition</strong>: + * <a href="http://en.wikipedia.org/wiki/Cryptographically_secure_pseudo-random_number_generator"> + * Secure Random Sequence</a></p> + * <p> + * <strong>Preconditions</strong>:<ul> + * <li><code>lower < upper</code> (otherwise an IllegalArgumentException + * is thrown.)</li> + * </ul></p> + * + * @param lower lower bound for generated integer + * @param upper upper bound for generated integer + * @return a random integer greater than or equal to <code>lower</code> + * and less than or equal to <code>upper</code>. + */ + int nextSecureInt(int lower, int upper); + + /** + * Generates a random long integer between <code>lower</code> + * and <code>upper</code> (endpoints included). + * <p> + * Sequences of long values generated using this method will be + * cryptographically secure. If cryptographic security is not required, + * <code>nextLong</code> should be used instead of this method.</p> + * <p> + * <strong>Definition</strong>: + * <a href="http://en.wikipedia.org/wiki/Cryptographically_secure_pseudo-random_number_generator"> + * Secure Random Sequence</a></p> + * <p> + * <strong>Preconditions</strong>:<ul> + * <li><code>lower < upper</code> (otherwise an IllegalArgumentException + * is thrown.)</li> + * </ul></p> + * + * @param lower lower bound for generated integer + * @param upper upper bound for generated integer + * @return a long integer greater than or equal to <code>lower</code> + * and less than or equal to <code>upper</code>. + */ + long nextSecureLong(long lower, long upper); + + /** + * Generates a random value from the Poisson distribution with + * the given mean. + * <p> + * <strong>Definition</strong>: + * <a href="http://www.itl.nist.gov/div898/handbook/eda/section3/eda366j.htm"> + * Poisson Distribution</a></p> + * <p> + * <strong>Preconditions</strong>: <ul> + * <li>The specified mean <i>must</i> be positive (otherwise an + * IllegalArgumentException is thrown.)</li> + * </ul></p> + * @param mean Mean of the distribution + * @return poisson deviate with the specified mean + */ + long nextPoisson(double mean); + + /** + * Generates a random value from the + * Normal (or Gaussian) distribution with the given mean + * and standard deviation. + * <p> + * <strong>Definition</strong>: + * <a href="http://www.itl.nist.gov/div898/handbook/eda/section3/eda3661.htm"> + * Normal Distribution</a></p> + * <p> + * <strong>Preconditions</strong>: <ul> + * <li><code>sigma > 0</code> (otherwise an IllegalArgumentException + * is thrown.)</li> + * </ul></p> + * @param mu Mean of the distribution + * @param sigma Standard deviation of the distribution + * @return random value from Gaussian distribution with mean = mu, + * standard deviation = sigma + */ + double nextGaussian(double mu, double sigma); + + /** + * Generates a random value from the exponential distribution + * with expected value = <code>mean</code>. + * <p> + * <strong>Definition</strong>: + * <a href="http://www.itl.nist.gov/div898/handbook/eda/section3/eda3667.htm"> + * Exponential Distribution</a></p> + * <p> + * <strong>Preconditions</strong>: <ul> + * <li><code>mu >= 0</code> (otherwise an IllegalArgumentException + * is thrown.)</li> + * </ul></p> + * @param mean Mean of the distribution + * @return random value from exponential distribution + */ + double nextExponential(double mean); + + /** + * Generates a uniformly distributed random value from the open interval + * (<code>lower</code>,<code>upper</code>) (i.e., endpoints excluded). + * <p> + * <strong>Definition</strong>: + * <a href="http://www.itl.nist.gov/div898/handbook/eda/section3/eda3662.htm"> + * Uniform Distribution</a> <code>lower</code> and + * <code>upper - lower</code> are the + * <a href = "http://www.itl.nist.gov/div898/handbook/eda/section3/eda364.htm"> + * location and scale parameters</a>, respectively.</p> + * <p> + * <strong>Preconditions</strong>:<ul> + * <li><code>lower < upper</code> (otherwise an IllegalArgumentException + * is thrown.)</li> + * </ul></p> + * + * @param lower lower endpoint of the interval of support + * @param upper upper endpoint of the interval of support + * @return uniformly distributed random value between lower + * and upper (exclusive) + */ + double nextUniform(double lower, double upper); + + /** + * Generates an integer array of length <code>k</code> whose entries + * are selected randomly, without repetition, from the integers <code> + * 0 through n-1</code> (inclusive). + * <p> + * Generated arrays represent permutations + * of <code>n</code> taken <code>k</code> at a time.</p> + * <p> + * <strong>Preconditions:</strong><ul> + * <li> <code>k <= n</code></li> + * <li> <code>n > 0</code> </li> + * </ul> + * If the preconditions are not met, an IllegalArgumentException is + * thrown.</p> + * + * @param n domain of the permutation + * @param k size of the permutation + * @return random k-permutation of n + */ + int[] nextPermutation(int n, int k); + + /** + * Returns an array of <code>k</code> objects selected randomly + * from the Collection <code>c</code>. + * <p> + * Sampling from <code>c</code> + * is without replacement; but if <code>c</code> contains identical + * objects, the sample may include repeats. If all elements of <code> + * c</code> are distinct, the resulting object array represents a + * <a href="http://rkb.home.cern.ch/rkb/AN16pp/node250.html#SECTION0002500000000000000000"> + * Simple Random Sample</a> of size + * <code>k</code> from the elements of <code>c</code>.</p> + * <p> + * <strong>Preconditions:</strong><ul> + * <li> k must be less than or equal to the size of c </li> + * <li> c must not be empty </li> + * </ul> + * If the preconditions are not met, an IllegalArgumentException is + * thrown.</p> + * + * @param c collection to be sampled + * @param k size of the sample + * @return random sample of k elements from c + */ + Object[] nextSample(Collection<?> c, int k); +} |