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Added allocations sample and updated README to mention instructions to fix performance issue
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‎allocations/README.md‎

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Sample to show allocations in Java Flight Recording
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=================================================
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This program checks whether a number is prime.
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Run the program without any arguments and also make a profiling recording.
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For example:
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`java -Xms64m -Xmx64m -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:StartFlightRecording=settings=profile,duration=30s,name=Allocations,filename=allocations.jfr -XX:FlightRecorderOptions=loglevel=info -jar target/allocations.jar`
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In Memory -> Allocation tab, you should see a high allocation rate.
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Also see Memory -> Garbage Collections tab and check the frequency of
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Try the program again after changing `Long` types to primitive `long`
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Run the program without locks.
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`java -Xms64m -Xmx64m -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:StartFlightRecording=settings=profile,duration=30s,name=Allocations,filename=allocations-fixed.jfr -XX:FlightRecorderOptions=loglevel=info -jar target/allocations.jar`

‎allocations/pom.xml‎

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<?xml version="1.0" encoding="utf-8"?>
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<!--
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# Copyright 2017 M. Isuru Tharanga Chrishantha Perera
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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-->
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<parent>
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<groupId>com.github.chrishantha.sample</groupId>
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<artifactId>java-samples</artifactId>
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<version>0.0.2-SNAPSHOT</version>
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<relativePath>../pom.xml</relativePath>
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</parent>
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<modelVersion>4.0.0</modelVersion>
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<artifactId>allocations</artifactId>
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<packaging>jar</packaging>
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<name>allocations</name>
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<dependencies>
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<dependency>
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<groupId>com.beust</groupId>
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<artifactId>jcommander</artifactId>
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</dependency>
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</dependencies>
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<properties>
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<fully.qualified.main.class>com.github.chrishantha.sample.allocations.App</fully.qualified.main.class>
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</properties>
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</project>

‎allocations/src/main/java/com/github/chrishantha/sample/allocations/App.java‎

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/*
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* Copyright 2017 M. Isuru Tharanga Chrishantha Perera
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.github.chrishantha.sample.allocations;
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import com.beust.jcommander.JCommander;
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import com.beust.jcommander.Parameter;
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public class App {
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@Parameter(names = "--max", description = "Max Numbers")
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private long max = 10_000_000L;
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@Parameter(names = "--help", description = "Display Help", help = true)
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private boolean help;
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public static void main(String[] args) {
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App app = new App();
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final JCommander jcmdr = new JCommander(app);
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jcmdr.setProgramName(App.class.getSimpleName());
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jcmdr.parse(args);
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System.out.println(app);
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if (app.help) {
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jcmdr.usage();
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return;
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}
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app.start();
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}
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boolean isPrime(Long n) {
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//check if n is a multiple of 2
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if (n % 2 == 0) return false;
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//if not, then just check the odds
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for (int i = 3; i * i <= n; i += 2) {
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if (n % i == 0)
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return false;
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}
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return true;
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}
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private void start() {
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Long primeCount = 0L;
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for (long i = 0; i < max; i++) {
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if (isPrime(i)) {
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primeCount++;
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}
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}
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System.out.format("Found %d prime numbers%n", primeCount);
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}
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@Override
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public String toString() {
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StringBuilder builder = new StringBuilder();
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builder.append("App [max=");
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builder.append(max);
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builder.append("]");
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return builder.toString();
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}
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}

‎hotmethods/README.md‎

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The contains methods in Linked List checks all the items. Algorithm run time is O(n). However the HashSet contains algorithm's run time is O(1).
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In the program, change `Collection<Integer> primeNumbers = new LinkedList<>()` to `Collection<Integer> primeNumbers = new HashSet<>()` to use a HashSet for Prime Numbers
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Check the runtime using HashSet.
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`java -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:StartFlightRecording=settings=profile,duration=60s,name=Hotmethods,filename=hotmethods.jfr -XX:FlightRecorderOptions=loglevel=info -jar target/hotmethods.jar --use-set`
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`java -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:StartFlightRecording=settings=profile,duration=60s,name=Hotmethods,filename=hotmethods-fixed.jfr -XX:FlightRecorderOptions=loglevel=info -jar target/hotmethods.jar`
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Use `time` command in Linux to measure the time.

‎hotmethods/src/main/java/com/github/chrishantha/sample/hotmethods/App.java‎

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import com.beust.jcommander.Parameter;
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import java.util.Collection;
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import java.util.HashSet;
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import java.util.LinkedList;
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import java.util.Random;
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@Parameter(names = "--max", description = "Maximum limit to generate prime numbers")
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private int max = 100000;
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@Parameter(names = "--use-set", description = "Use Hash Set for Prime Numbers", arity = 0)
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private boolean useSet;
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@Parameter(names = "--help", description = "Display Help", help = true)
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private boolean help;
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}
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private void start() {
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Collection<Integer> primeNumbers = useSet ? new HashSet<>() : new LinkedList<>();
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Collection<Integer> primeNumbers = new LinkedList<>();
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System.out.println("Generating Prime numbers between 1 and " + max);
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for (int i = 1; i < max; i++) {
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boolean isPrimeNumber = true;
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builder.append(randomNumbersCount);
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builder.append(", max=");
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builder.append(max);
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builder.append(", useSet=");
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builder.append(useSet);
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builder.append("]");
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return builder.toString();
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}

‎latencies/README.md‎

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Since there is no shared resource, you can avoid the lock and improve the performance.
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Remove the `synchronized` keyword in `isEven` method.
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Run the program without locks.
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`java -jar -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:StartFlightRecording=settings=profile,duration=30s,name=Latencies,filename=latencies-fixed.jfr -XX:FlightRecorderOptions=loglevel=info target/latencies.jar --lock false`
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`java -jar -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:StartFlightRecording=settings=profile,duration=30s,name=Latencies,filename=latencies-fixed.jfr -XX:FlightRecorderOptions=loglevel=info target/latencies.jar`

‎latencies/src/main/java/com/github/chrishantha/sample/latencies/App.java‎

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@Parameter(names = "--count", description = "Print Count")
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private int count = 50;
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@Parameter(names = "--lock", description = "Lock", arity = 1)
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private boolean lock = true;
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@Parameter(names = "--help", description = "Display Help", help = true)
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private boolean help;
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app.start();
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}
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private class EvenThread extends Thread {
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public EvenThread() {
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@Override
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public void run() {
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for (int i = 0; i < count; i++) {
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printEven(i);
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if (isEven(i)) {
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printNumber(i);
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}
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}
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}
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}
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@Override
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public void run() {
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for (int i = 0; i < count; i++) {
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printOdd(i);
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if (!isEven(i)) {
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printNumber(i);
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}
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}
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}
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}
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System.out.format("Thread: %s, Number: %d%n", Thread.currentThread().getName(), i);
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}
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private void printEven(int i) {
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if ((lock && isEvenLocked(i)) || isEven(i)) {
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printNumber(i);
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}
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}
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private void printOdd(int i) {
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if ((lock && !isEvenLocked(i)) || !isEven(i)) {
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printNumber(i);
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}
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}
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private synchronized boolean isEvenLocked(int i) {
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return isEven(i);
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}
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private boolean isEven(int i) {
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private synchronized boolean isEven(int i) {
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try {
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Thread.sleep(1000);
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} catch (InterruptedException e) {

‎pom.xml‎

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<module>highcpu</module>
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<module>hotmethods</module>
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<module>latencies</module>
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<module>allocations</module>
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</modules>
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<dependencyManagement>

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