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Java 14 examples
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‎.gitignore‎

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hs_err_pid*
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.vscode/
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.DS_Store
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*.data
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*.data
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jdt.ls-java-project/
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*.dmg

‎java-14/HelpfulNPEMessages.java‎

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import static java.util.stream.Collectors.toList;
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import java.util.stream.IntStream;
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/**
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* To run: `java -XX:+ShowCodeDetailsInExceptionMessages HelpfulNPEMessages.java`
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*/
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public class HelpfulNPEMessages {
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public static void main(String[] args) {
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simpleObjectAccess();
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insideStreams();
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}
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private static void simpleObjectAccess() {
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System.out.println("=== Simple Object Attribute Access ===");
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try {
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var thing = new Thing(11);
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System.out.println("Value " + thing.weight.value);
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} catch (NullPointerException ex) {
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ex.printStackTrace();
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}
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}
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private static void insideStreams() {
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System.out.println("%n=== Attribute Access Inside Streams ===");
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try {
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IntStream.of(2, 4, 6, 8, 9)
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.mapToObj(Thing::new)
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.map(thing -> thing.weight.value)
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.forEach(v -> System.out.println("Val " + v));
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} catch (NullPointerException ex) {
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ex.printStackTrace();
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}
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}
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}
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class Thing {
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Weight weight;
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Thing(int weight) {
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if (weight % 2 == 0) {
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this.weight = new Weight(weight);
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}
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}
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public Weight getWeight() {
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return weight;
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}
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}
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class Weight {
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Integer value;
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Weight(int value) {
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if (value % 2 == 0) {
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this.value = value;
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}
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}
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public int getValue() {
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return value;
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}
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}

‎java-14/JFREventStreamTest.java‎

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import java.time.Duration;
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import java.util.stream.IntStream;
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import java.util.ArrayList;
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import jdk.jfr.consumer.RecordingStream;
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/***
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* The profiles configurations is stored in: `$JAVA_HOME/lib/jrf/`
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*/
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public class JFREventStreamTest {
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public static void main(String[] args) throws InterruptedException {
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var task = new FibonacciCalculator(Thread.currentThread());
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var thread = new Thread(task, "t-fib");
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thread.start();
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try (var rs = new RecordingStream()) {
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rs.enable("jdk.CPULoad").withPeriod(Duration.ofSeconds(1));
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rs.enable("jdk.GarbageCollection").withPeriod(Duration.ofSeconds(1));
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rs.enable("jdk.GCHeapSummary").withPeriod(Duration.ofSeconds(1));
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rs.onEvent("jdk.CPULoad", event -> {
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System.out.printf("\tCPU load: %f%% - %f%%%n",
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(event.getFloat("jvmUser") * 100),
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(event.getFloat("machineTotal") * 100)
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);
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});
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rs.onEvent("jdk.GCHeapSummary", event -> {
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System.out.printf("\tGC - Summary - %s %f MB%n",
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event.getString("when"),
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(event.getFloat("heapUsed") / 1_000_000)
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);
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});
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rs.onEvent("jdk.GarbageCollection", event -> {
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System.out.printf("\tGC - Cause %s - Durantion: %.04fms%n", event.getString("cause"), (event.getFloat("duration") / 1_000_000));
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});
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rs.startAsync();
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thread.join();
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}
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}
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}
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class FibonacciCalculator implements Runnable {
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private Thread thread;
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FibonacciCalculator(Thread thread) {
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this.thread = thread;
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}
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public void run() {
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System.out.println("Starting calculation");
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int number = 40;
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while (true) {
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System.out.println("Calculating for " + number);
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var result = calculate(number);
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System.out.println("Result for " + number + " is " + result);
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if (!thread.isAlive()) {
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System.out.println("Ending calculation");
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break;
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}
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number += 5;
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}
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}
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/**
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* Bad implementation to take much time.
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*/
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public long calculate(int n) {
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if (n <= 1)
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return 1;
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var list = new ArrayList<>(n);
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IntStream.range(0, n).forEach(__ -> list.add(new Object()));
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return calculate(n - 1) + calculate(n - 2);
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}
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}

‎java-14/PackagingTool.java‎

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import javax.swing.JOptionPane;
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/**
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* Steps:
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*
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* - compile: `javac PackagingTool.java`
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* - create JAR: `jar -cfe packaging-tool-example.jar PackagingTool PackagingTool.class`
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* - test JAR: `java -jar packaging-tool-example.jar`
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* - create the Package: `jpackage --name pack-tool-sample --input . --main-jar packaging-tool-example.jar --main-class PackagingTool`
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*
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* Package will generate:
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* - `dmg` on macOS
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* - `msi` on Windows
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* - `app` on Linux
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*/
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public class PackagingTool {
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public static void main(String[] args) {
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System.out.println("Main =)");
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JOptionPane.showMessageDialog(null, "Hello world from self-contained application", null,
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JOptionPane.INFORMATION_MESSAGE);
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}
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}

‎java-14/README.md‎

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* Promotion to standard
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* Text blocks improvements
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* added new flags
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* Patttern matching for `instanceof`
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* Patttern matching for `instanceof`
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* added as Preview
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* Records
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* added as Preview
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* Helpful NullPointerExpections
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* flag to enable: `-XX:+ShowCodeDetailsInExceptionMessages`
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* Packaging tool to create self-contained Java applications
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* bin: `jpackage`
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* JFR Event Stream
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* [Here](https://github.com/flight-recorder/health-report) is a great example of a tool built
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## JEPs
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