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* Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package java.util.random;
import java.util.function.Function;
import java.util.Map;
import java.util.Objects;
import java.util.ServiceLoader;
import java.util.ServiceLoader.Provider;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
* This is a factory class for generating random number generators of a specific
* catagory and algorithm.
*/
public class RandomGeneratorFactory<T> {
/**
* Instance provider class of random number algorithm.
*/
private final Provider<T> provider;
/**
* Map of provider classes.
*/
private static Map<String, Provider<RandomGenerator>> providerMap;
/**
* Private constructor.
*
* @param provider Provider class to wrap.
*/
private RandomGeneratorFactory(Provider<T> provider) {
this.provider = provider;
}
/**
* Returns the provider map, lazily constructing map on first call.
*
* @return Map of provider classes.
*/
private static Map<String, Provider<RandomGenerator>> getProviderMap() {
if (providerMap == null) {
synchronized (RandomGeneratorFactory.class) {
if (providerMap == null) {
providerMap =
ServiceLoader
.load(RandomGenerator.class)
.stream()
.filter(p -> !p.type().isInterface())
.collect(Collectors.toMap(p -> p.type().getSimpleName().toUpperCase(),
Function.identity()));
}
}
}
return providerMap;
}
private static Provider<RandomGenerator> findProvider(String name, Class<? extends RandomGenerator> category)
throws IllegalArgumentException {
Map<String, Provider<RandomGenerator>> pm = getProviderMap();
Provider<RandomGenerator> provider = pm.get(name.toUpperCase());
if (provider == null || provider.type().isAssignableFrom(category)) {
throw new IllegalArgumentException(name + " is an unknown random number generator");
}
return provider;
}
/**
* Returns a {@link RandomGenerator} that utilizes the {@code name} algorithm.
*
* @param name Name of random number algorithm to use
* @param category Sub-interface of {@link RandomGenerator} to type check
* @param <T> Sub-interface of {@link RandomGenerator} to produce
* @return An instance of {@link RandomGenerator}
* @throws IllegalArgumentException when either the name or category is null
*/
static <T> T of(String name, Class<? extends RandomGenerator> category)
throws IllegalArgumentException {
@SuppressWarnings("unchecked")
T uncheckedRandomGenerator = (T)findProvider(name, category).get();
return uncheckedRandomGenerator;
}
/**
* Returns a {@link RandomGeneratorFactory} that will produce instances
* of {@link RandomGenerator} that utilizes the {@code name} algorithm.
*
* @param name Name of random number algorithm to use
* @param category Sub-interface of {@link RandomGenerator} to type check
* @param <T> Sub-interface of {@link RandomGenerator} to produce
* @return Factory of {@link RandomGenerator}
* @throws IllegalArgumentException when either the name or category is null
*/
static <T> RandomGeneratorFactory<T> factoryOf(String name, Class<? extends RandomGenerator> category)
throws IllegalArgumentException {
@SuppressWarnings("unchecked")
Provider<T> uncheckedProvider = (Provider<T>)findProvider(name, category);
return new RandomGeneratorFactory<T>(uncheckedProvider);
}
/**
* Create an instance of {@link RandomGenerator}.
*
* @return Instance of {@link RandomGenerator}.
*/
public T create() {
return provider.get();
}
}