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Java example source code file (BaseRuleFactoryTest.java)

This example Java source code file (BaseRuleFactoryTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

always, atomicinteger, baserulefactory, baserulefactorytest, callable, double, dummyrulefactory, future, interruptedexception, list, pair, rulebuilder, threading, threadpoolexecutor, threads, unexpected, util

The BaseRuleFactoryTest.java Java example source code

 * 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.
package org.apache.commons.math3.analysis.integration.gauss;

import java.util.List;
import java.util.ArrayList;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.Callable;
import java.util.concurrent.Future;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.commons.math3.util.Pair;
import org.junit.Test;
import org.junit.Assert;

 * Test for {@link BaseRuleFactory}.
public class BaseRuleFactoryTest {
     * Tests that a given rule rule will be computed and added once to the cache
     * whatever the number of times this rule is called concurrently.
        public void testConcurrentCreation() throws InterruptedException,
                                                    ExecutionException {
        // Number of times the same rule will be called.
        final int numTasks = 20;

        final ThreadPoolExecutor exec
            = new ThreadPoolExecutor(3, numTasks, 1, TimeUnit.SECONDS,
                                     new ArrayBlockingQueue<Runnable>(2));

        final List<Future> results
            = new ArrayList<Future>();
        for (int i = 0; i < numTasks; i++) {
            results.add(exec.submit(new RuleBuilder()));

        // Ensure that all computations have completed.
        for (Future<Pair f : results) {

        // Assertion would fail if "getRuleInternal" were not "synchronized".
        final int n = RuleBuilder.getNumberOfCalls();
        Assert.assertEquals("Rule computation was called " + n + " times", 1, n);

class RuleBuilder implements Callable<Pair {
    private static final DummyRuleFactory factory = new DummyRuleFactory();

    public Pair<double[], double[]> call() {
        final int dummy = 2; // Always request the same rule.
        return factory.getRule(dummy);

    public static int getNumberOfCalls() {
        return factory.getNumberOfCalls();

class DummyRuleFactory extends BaseRuleFactory<Double> {
    /** Rule computations counter. */
    private static AtomicInteger nCalls = new AtomicInteger();

    protected Pair<Double[], Double[]> computeRule(int order) {
        // Tracks whether this computation has been called more than once.

        try {
            // Sleep to simulate computation time.
        } catch (InterruptedException e) {
            Assert.fail("Unexpected interruption");

         // Dummy rule (but contents must exist).
        final Double[] p = new Double[order];
        final Double[] w = new Double[order];
        for (int i = 0; i < order; i++) {
            p[i] = new Double(i);
            w[i] = new Double(i);
        return new Pair<Double[], Double[]>(p, w);

    public int getNumberOfCalls() {
        return nCalls.get();

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