Claudenw commented on a change in pull request #258: URL: https://github.com/apache/commons-collections/pull/258#discussion_r798321300
########## File path: src/main/java/org/apache/commons/collections4/bloomfilter/Shape.java ########## @@ -0,0 +1,486 @@ +/* + * 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.collections4.bloomfilter; + +import java.util.Objects; + +/** + * The definition of a Bloom filter shape. + * + * <p> This class contains the values for the filter configuration and is used to + * convert a Hasher into a BloomFilter as well as verify that two Bloom filters are + * compatible. (i.e. can be compared or merged)</p> + * + * <h2>Interrelatedness of values</h2> + * + * <dl> <dt>Number of Items ({@code n})</dt> + * <dd>{@code n = ceil(m / (-k / ln(1 - exp(ln(p) / k))))}</dd> <dt>Probability of + * False Positives ({@code p})</dt> <dd>{@code p = pow(1 - exp(-k / (m / n)), k)}</dd> <dt>Number + * of Bits ({@code m})</dt> + * <dd>{@code m = ceil((n * ln(p)) / ln(1 / pow(2, ln(2))))}</dd> <dt>Number of + * Functions ({@code k})</dt> <dd>{@code k = round((m / n) * ln(2))}</dd> </dl> + * + * @see <a href="http://hur.st/bloomfilter?n=3&p=1.0E-5";>Bloom Filter calculator</a> + * @see <a href="https://en.wikipedia.org/wiki/Bloom_filter";>Bloom filter + * [Wikipedia]</a> + * @since 4.5 + */ +public final class Shape implements Comparable<Shape> { + + /** + * Number of hash functions to create a filter ({@code k}). + */ + private final int numberOfHashFunctions; + + /** + * Number of bits in the filter ({@code m}). + */ + private final int numberOfBits; + + /** + * Constructs a filter configuration with the specified number of items ({@code n}) and Review comment: Shape constructor was made private and a `fromNK()` method added to match the methods move out of factory. The Factory class was removed and the `fromX()` method added to Shape so all Shape construction is no of the form `fromX()` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
