HerbstCampus2020: Eine Reise durch die JDKs

Viele von Euch, so wie ich, arbeiten im Job noch mit JDK 8. Daher möchte ich Euch mitnehmen auf die Reise durch die JDKs. Wir starten unsere Reise bei JDK 8 und wandern bis zur aktuellen Version. Außerdem wagen wir einen Blick auf die Attraktionen der zukünftigen Versionen.
Wir halten unter anderem an folgenden Stationen:
- JShell
- Private Methods in Interfaces
- Optional class
- Reservierter Typ "var"
- Erweiterung der Collections
- HttpClient/HttpRequest neues FluentAPI
- Switch Expressions
- Erweiterung der String-Klasse

Diese werden zum Teil anhand von Quelltext-Beispielen veranschaulicht.
Ich wünsche Euch eine gute Reise.

P.S.: Bringt festes Schuhwerk mit.

Transcript

1. @stgerberding
   Eine Reise durch die JDKs
   Sandra Gerberding – smartsteuer GmbH
   

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2. @stgerberding
   T
   ourguide
   Software-Entwicklerin:
   Java Web Anwendungen
   Continuous Integration
   Software-Architektur
   T
   witter:
   @stgerberding
   Blog:
   http://sandra.gerberding.blog
   E-Mail:
   sandra.gerberding@smartsteuer.de
   Speaker Deck:
   https://speakerdeck.com/sandrag
   Sandra Gerberding
   2
   

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3. @stgerberding
   JDK 8
   JDK 9
   JDK 10
   JDK 11
   JDK 12
   JDK 13
   JDK 14
   3
   

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4. @stgerberding
   JDK 8
   JDK 9
   JDK 10
   JDK 11
   JDK 12
   JDK 13
   JDK 14
   4
   

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5. @stgerberding
   JDK9
   JShell
   Jigsaw
   Private methods in interfaces
   Immutable Collections
   … und mehr …
   5
   

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6. @stgerberding
   JDK 9 - Jigsaw
   module tax.calculation {
   exports de.gerberding.tax.calculation.api;
   }
   module tax.client {
   requires tax.calculation;
   }
   module tax.calculation
   module tax.client
   package
   …tax.calculation.implementation
   package
   …tax.calculation.api
   package
   …tax.client
   module-info.java
   module-info.java
   6
   

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7. @stgerberding
   JDK 9 - Jigsaw
   package de.gerberding.tax.calculation.api;
   import de.gerberding.tax.calculation.implementation.SimpleTaxCalculator;
   public interface TaxCalculator {
   double computeVAT (double netPrice, double vatRate);
   double computeGrossPrice (double netPrice, double vatRate);
   static TaxCalculator createSimpleTaxCalculator () {
   return new SimpleTaxCalculator ();
   }
   } package de.gerberding.tax.calculation.implementation;
   import de.gerberding.tax.calculation.api.TaxCalculator;
   public class SimpleTaxCalculator implements TaxCalculator {
   @Override
   public double computeVAT (final double netPrice, final double vatRate) {
   return (netPrice / 100) * vatRate;
   }
   @Override
   public double computeGrossPrice (final double netPrice, final double vatRate) {
   return netPrice + computeVAT (netPrice, vatRate);
   }
   }
   module tax.calculation {
   exports de.gerberding.tax.calculation.api;
   }
   7
   

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8. @stgerberding
   JDK 9 - Jigsaw
   public class TaxCalculatorClient {
   public static void main (final String[] args) {
   final TaxCalculator taxCalculator = new SimpleTaxCalculator ();
   final double vat = taxCalculator.computeVAT (15.95, 19.00);
   final double grossPrice = taxCalculator.computeGrossPrice (20.45, 7);
   System.out.println ("---------- Tax Calculator ——————");
   System.out.println ("netPrice = 15.95 and vatRate = 19 => vat = " + vat);
   System.out.println ("netPrice = 20.45 and vatRate = 7 => grossPrice = " + grossPrice);
   }
   }
   module tax.client {
   requires tax.calculation;
   }
   public class TaxCalculatorClient {
   public static void main (final String[] args) {
   final TaxCalculator taxCalculator = TaxCalculator.createSimpleTaxCalculator ();
   final double vat = taxCalculator.computeVAT (15.95, 19.00);
   final double grossPrice = taxCalculator.computeGrossPrice (20.45, 7);
   System.out.println ("---------- Tax Calculator ------------");
   System.out.println ("netPrice = 15.95 and vatRate = 19 => vat = " + vat);
   System.out.println ("netPrice = 20.45 and vatRate = 7 => grossPrice = " + grossPrice);
   }
   }
   8
   

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9. @stgerberding
   JDK 9 - JShell
   jshell> Pattern.compile("(\\d{2})\\.(\\d{2})\\.(\\d{4})");
   $1 ==> (\d{2})\.(\d{2})\.(\d{4})
   | created scratch variable $1 : Pattern
   jshell> $1.matcher("02.09.2020");
   $2 ==> java.util.regex.Matcher[pattern=(\d{2})\.(\d{2})\.(\d{4}) region=0,10 lastmatch=]
   | created scratch variable $2 : Matcher
   jshell> $2.matches()
   $3 ==> true
   | created scratch variable $3 : boolean
   jshell> for (int group = 0; group <= $2.groupCount(); group++) {
   ...> System.out.println("group " + group + ": " + $2.group(group));
   ...> }
   group 0: 02.09.2020
   group 1: 02
   group 2: 09
   group 3: 2020
   9
   

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10. @stgerberding
    JDK 9 - JShell
    jshell> /list -all
    s1 : import java.io.*;
    s2 : import java.math.*;
    s3 : import java.net.*;
    s4 : import java.nio.file.*;
    s5 : import java.util.*;
    s6 : import java.util.concurrent.*;
    s7 : import java.util.function.*;
    s8 : import java.util.prefs.*;
    s9 : import java.util.regex.*;
    s10 : import java.util.stream.*;
    1 : Pattern.compile("(\\d{2})\\.(\\d{2})\\.(\\d{4})");
    2 : $1.matcher("02.09.2020");
    3 : $2.matches()
    4 : for (int group = 0; group <= $2.groupCount(); group++) {
    System.out.println("group " + group + ": " + $2.group(group));
    }
    https://docs.oracle.com/javase/9/jshell/toc.htm
    10
    

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11. @stgerberding
    JDK 9 - Private Methods in Interfaces
    public interface UserService {
    boolean isAllowed (User user, Right right);
    default List getRights (final User user) {
    final List userRights = new ArrayList<>();
    user.getRoles ().forEach ((Role role) -> {
    userRights.addAll(role.getRights());
    });
    return userRights;
    }
    }
    public interface UserService {
    boolean isAllowed (User user, Right right);
    default List getRights (final User user) {
    final List userRights = new ArrayList<>();
    addAllUserRights (user, userRights);
    return userRights;
    }
    private void addAllUserRights (final User user,
    final List userRights) {
    user.getRoles ().forEach ((Role role) -> {
    userRights.addAll(role.getRights());
    });
    }
    }
    11
    

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12. @stgerberding
    JDK 9 - Immutable Collections
    final List immutableLanguages = List.of ("Groovy", "Kotlin", "Java");
    final List languagesShort = Collections.unmodifiableList
    (Arrays.asList ("Groovy", "Kotlin", "Java"));
    final List languages = new ArrayList<>();
    languages.add ("Groovy");
    languages.add ("Kotlin");
    languages.add ("Java");
    final List unmodifiableLanguages = Collections.unmodifiableList (languages);
    final Map starTrekVessels = new HashMap<>();
    starTrekVessels.put (STAR_TREK, "NCC-1701");
    starTrekVessels.put (STAR_TREK_NG, "NCC-1701-D");
    starTrekVessels.put (STAR_TREK_VOYAGER, "NCC-74656");
    starTrekVessels.put (STAR_TREK_DS9, "NX-74205");
    final Map unmodifiableVessels = Collections.unmodifiableMap (starTrekVessels);
    final Map immutableVessels = Map.of (STAR_TREK, "NCC-1701",
    STAR_TREK_NG, "NCC-1701-D",
    STAR_TREK_VOYAGER, "NCC-74656",
    STAR_TREK_DS9, "NX-74205");
    JDK 8
    JDK 9
    JDK 8
    JDK 9
    List
    Map
    12
    

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13. @stgerberding
    JDK 9 … und mehr …
    - 2 neue Interfaces im Process API
    - java.jang.ProcessHandle
    - Java.jang.ProcessHandleInfo
    - Verbesserung von try with Resources
    - Completable Future API
    - Support delays and timeouts
    - Unicode 8
    - String Optimierung (Speicherplatz)
    - JavaDoc erzeugt HTML 5
    - Unterstützung von PKC512 in Keystores
    - Diamond Operator in anonymen Classes
    - Und mehr …
    https://docs.oracle.com/javase/9/whatsnew/toc.htm
    13
    

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14. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    14
    

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15. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    15
    

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16. @stgerberding
    JDK10
    Reserved T
    ype „var“
    Release
    Docker Support
    Collections
    … und mehr …
    16
    

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17. @stgerberding
    JDK 10 - Reserved T
    ype „var“
    public class VarDemo {
    final var memberVariable = "Wej Qap!";
    public static void main (final String[] args) {
    var localVariable; // QoHbe' SuS!
    String var;
    var personsVar = new ArrayList<>(); // ArrayList != List
    List persons = new ArrayList<>();
    var authorVar = getAuthor (); // Return value: Person? Author? …?
    Person author = getAuthor ();
    }
    }
    var message = "Hello World!"; // String message = "Hello World!";
    message = 1234;
    var person = new Person ("Gene", "Roddenberry");
    17
    

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18. @stgerberding
    JDK 10 - Docker Support
    Host RAM
    Docker Container RAM
    JVM in Docker Container RAM
    32 GByte
    6 GByte
    8 GByte Standard Wert 25% des Hosts
    Vor JDK 10
    JVM in Docker Container RAM
    1,5 GByte Standard Wert 25% des Docker Containers
    Ab JDK 10
    Aus Designgründen sind die Größen nicht proportional dargestellt.
    18
    

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19. @stgerberding
    JDK 10 - Docker Support
    Host CPUs
    Docker Container CPUs
    JVM in Docker Container CPUs
    6 CPUs
    3 CPUs
    6 CPUs Standard Wert 100% des Hosts
    Vor JDK 10
    JVM in Docker Container RAM
    3 CPUs Standard Wert 100% des Docker Containers
    Ab JDK 10
    19
    

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20. @stgerberding
    JDK 10 - Collections
    final List names = getNames ();
    final List immutableCopyOfNames = List.copyOf (names);
    System.out.println ("immutableCopyOfList type: " + immutableCopyOfNames.getClass ());
    final Set colors = getColors ();
    final Set immutableCopyOfColors = Set.copyOf (colors);
    System.out.println ("immutableCopyOfSet type: " + immutableCopyOfColors.getClass ());
    final Map personAgeMapping = getPersonsAge ();
    final Map immutableCopyOfMap = Map.copyOf (personAgeMapping);
    System.out.println ("immutableCopyOfMap type: " + immutableCopyOfMap.getClass ());
    final List immutableNames = names.stream ().collect (Collectors.toUnmodifiableList ());
    System.out.println ("immutableNames type: " + immutableNames.getClass ());
    immutableCopyOfList type: class java.util.ImmutableCollections$ListN
    immutableCopyOfSet type: class java.util.ImmutableCollections$SetN
    immutableCopyOfMap type: class java.util.ImmutableCollections$MapN
    immutableNames type: class java.util.ImmutableCollections$ListN
    Console
    20
    

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21. @stgerberding
    JDK 10… und mehr …
    - Optional Erweiterung
    - Optional.orElseThrow ()
    - JavaDoc Erweiterungen (css ..)
    - javah entfernt
    - Und mehr …
    https://www.oracle.com/java/technologies/javase/10-relnote-issues.html
    21
    

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22. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    22
    

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23. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    23
    

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24. @stgerberding
    JDK11
    L
    TS
    API Änderungen
    JCMD / Flight Recorder
    HTTP Client
    Collections
    … und mehr …
    24
    

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25. @stgerberding
    JDK 11 - JCMD/Flight Recorder
    sandragerberding@MacBook-Pro demo % jcmd 18743 VM.flags
    18743:
    -XX:-BytecodeVerificationLocal -XX:-BytecodeVerificationRemote -XX:CICompilerCount=12
    -XX:ConcGCThreads=3 -XX:G1ConcRefinementThreads=13 -XX:G1HeapRegionSize=4194304
    -XX:GCDrainStackTargetSize=64 -XX:InitialHeapSize=1073741824 -XX:+ManagementServer
    -XX:MarkStackSize=4194304 -XX:MaxHeapSize=17179869184 -XX:MaxNewSize=10305404928
    -XX:MinHeapDeltaBytes=4194304 -XX:NonNMethodCodeHeapSize=12163472 -XX:NonProfiledCodeHeapSize=239494768
    -XX:ProfiledCodeHeapSize=0 -XX:ReservedCodeCacheSize=251658240 -XX:+SegmentedCodeCache
    -XX:TieredStopAtLevel=1 -XX:+UseCompressedClassPointers -XX:+UseCompressedOops
    -XX:+UseG1GC
    25
    

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26. @stgerberding
    JDK 11 - JCMD/Flight Recorder
    26
    

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27. @stgerberding
    JDK 11 - JCMD/Flight Recorder
    27
    

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28. @stgerberding
    JDK 11 - String - API Änderungen
    System.out.println ("Character: " + Character.toString (65));
    System.out.println ("•".repeat (20));
    final String blank = " ";
    System.out.println ("'" + blank + "'.isBlank: " + blank.isBlank ());
    System.out.println ("'" + blank + "'.isEmpty: " + blank.isEmpty ());
    System.out.println ("•".repeat (20));
    final String string = " \u205Fnaked\u205F ";
    System.out.println ("strip String: '" + string.strip () + "'");
    System.out.println ("trim String: '" + string.trim () + "'");
    System.out.println ("•".repeat (20));
    "a\nb\nc\nd\ne\nf".lines ().forEach (line -> System.out.println ("line = " + line));
    Character: A
    ••••••••••••••••••••
    ' '.isBlank: true
    ' '.isEmpty: false
    ••••••••••••••••••••
    strip String: 'naked'
    trim String: ' naked '
    ••••••••••••••••••••
    line = a
    line = b
    line = c
    28
    

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29. @stgerberding
    JDK 11 - HTTP Client
    final URL url = new URL ("https://swapi.dev/api/planets/2/");
    final HttpURLConnection connection = (HttpURLConnection) url.openConnection ();
    connection.setRequestMethod ("GET");
    connection.setRequestProperty ("Accept", "application/json");
    final int responseCode = connection.getResponseCode ();
    final Map> headers = connection.getHeaderFields ();
    final BufferedReader in = new BufferedReader (new InputStreamReader (connection.getInputStream ()));
    String inputLine;
    final StringBuilder responseBody = new StringBuilder ();
    while ((inputLine = in.readLine ()) != null) {
    responseBody.append (inputLine);
    }
    in.close ();
    connection.disconnect ();
    System.out.println ("Status: " + responseCode);
    System.out.println ("Body: " + responseBody);
    System.out.println ("Headers: " + headers);
    JDK 8 altes API
    29
    

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30. @stgerberding
    final URI uri = new URI ("https://swapi.dev/api/planets/1/");
    final HttpRequest request = HttpRequest.newBuilder (uri).GET ().build ();
    final HttpResponse.BodyHandler bodyHandler = HttpResponse.BodyHandlers.ofString ();
    final HttpClient httpClient = HttpClient.newBuilder ().build ();
    final HttpResponse response = httpClient.send (request, bodyHandler);
    final int responseCode = response.statusCode ();
    final String responseBody = response.body ();
    final HttpHeaders headers = response.headers ();
    System.out.println ("Status: " + responseCode);
    System.out.println ("Body: " + responseBody);
    System.out.println ("Headers: " + headers.map ());
    JDK 11 - HTTP Client
    JDK 11 neues API
    30
    

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31. @stgerberding
    JDK 11… und mehr …
    - T
    ransport Layer Security (TLS) 1.3
    - „var“ Erweiterung
    - auch als Lambda Parameter
    - Unicode 10
    - Applet, JavaFX … nicht mehr Bestandteil vom JDK 11
    - Und mehr …
    https://www.oracle.com/java/technologies/javase/jdk-11-relnote.html
    31
    

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32. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    32
    

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33. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    33
    

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34. @stgerberding
    JDK12
    Switch Expression
    … und mehr …
    Preview
    34
    

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35. @stgerberding
    JDK 12 … und mehr …
    - Kleine Änderungen
    - Unicode 11
    https://www.oracle.com/java/technologies/javase/12-relnote-issues.html
    35
    

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36. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    36
    

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37. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    37
    

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38. @stgerberding
    JDK13
    Switch Expression
    T
    ext Blocks
    … und mehr …
    Preview
    Preview
    38
    

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39. @stgerberding
    JDK 13 … und mehr …
    - FileSystems API hat 3 neue Methods
    - newFileSystem(Path)
    - newFileSystem(Path, Map)
    - newFileSystem(Path, Map, ClassLoader)
    - Unicode 12.1
    - Und mehr …
    https://www.oracle.com/java/technologies/javase/13-relnote-issues.html
    39
    

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40. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    40
    

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41. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    41
    

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42. @stgerberding
    JDK14
    Switch Expression
    Records
    … und mehr …
    Preview
    42
    

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43. @stgerberding
    JDK 14 - Switch Expressions
    public String findGalaxyQuadrant (final Species species) {
    String quadrant;
    switch (species) {
    case KLINGONS:
    case ROMULANS:
    quadrant = "Beta quadrant";
    break;
    case FERENGI:
    case VULCANS:
    case HUMANS:
    quadrant = "Alpha quadrant";
    break;
    default:
    quadrant = "unknown quadrant";
    break;
    }
    return quadrant;
    }
    public String findGalaxyQuadrant (final Species species) {
    String quadrant;
    switch (species) {
    case KLINGONS,
    ROMULANS -> quadrant = "Beta quadrant";
    case FERENGI,
    VULCANS,
    HUMANS -> quadrant = "Alpha quadrant";
    default -> quadrant = "unknown quadrant";
    }
    return quadrant;
    }
    public String findGalaxyQuadrant (final Species species) {
    return switch (species) {
    case KLINGONS,
    ROMULANS -> "Beta quadrant";
    case FERENGI,
    VULCANS,
    HUMANS -> "Alpha quadrant";
    default -> "unknown quadrant";
    };
    }
    enum Species {
    KLINGONS, ROMULANS, FERENGI, VULCANS, HUMANS, BORG
    }
    Classic Switch Statement
    New Switch Statement
    New Switch Expression
    43
    

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44. @stgerberding
    JDK 14 - Switch Expressions
    public String findGalaxyQuadrant (final Species species) {
    switch (species) {
    case KLINGONS,
    ROMULANS -> { return "Beta quadrant"; }
    case FERENGI,
    VULCANS,
    HUMANS -> { return "Alpha quadrant"; }
    default -> { return "unknown quadrant"; }
    }
    }
    public int computeNumberOfIndividuals (final Species species) {
    return switch (species) {
    case KLINGONS -> {
    final int individualsAlpha = calculateIndividualsPerQuadrant (KLINGONS, "Alpha");
    final int individualsBeta = calculateIndividualsPerQuadrant (KLINGONS, "Beta");
    yield individualsAlpha + individualsBeta;
    }
    case HUMANS -> calculateIndividualsPerQuadrant (HUMANS, "Alpha");
    default -> 0;
    };
    }
    New Switch Statement with return
    New Switch Expression with yield
    44
    

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45. @stgerberding
    JDK 14 … und mehr …
    - Detaillierte NullPointerException Message mit JVM Option aktivierbar
    - TLS Erweiterungen
    - Und mehr …
    https://www.oracle.com/java/technologies/javase/14-relnote-issues.html
    45
    

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46. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    46
    

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47. @stgerberding
    JDK 8
    JDK 9
    JDK 10
    JDK 11
    JDK 12
    JDK 13
    JDK 14
    47
    

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48. @stgerberding
    JDK15
    Sealed T
    ypes
    Records
    Pattern Matching for instanceof
    T
    ext Blocks
    … und mehr …
    Preview
    Preview
    Preview
    48
    

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49. @stgerberding
    JDK 15 - T
    ext Blocks
    final String exampleText =
    "Das ist ein\n" +
    " \"Beispiel\" Text!\n" +
    "Das ist ein etwas längerer Text und ich möchte ihn nur in der 'IDE' umbrechen. ";
    final String exampleText = """
    Das ist ein
    "Beispiel" Text!
    Das ist ein etwas längerer Text \
    und ich möchte ihn nur in der 'IDE' umbrechen. \s""";
    'Das ist ein
    "Beispiel" Text!
    Das ist ein etwas längerer Text und ich möchte ihn nur in der 'IDE' umbrechen. '
    Console
    49
    

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50. @stgerberding
    JDK 15 … und mehr …
    - CharSequence Erweiterung
    - Default Method
    CharSequence.isEmpty ()
    - Hidden Classes
    - Unicode 13.0
    - Nashorn Engine ist nicht mehr
    Bestandteil es JDKs
    - TLS Erweiterungen
    - Und mehr …
    https://jdk.java.net/15/release-notes
    50
    

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51. @stgerberding
    Vielen Dank
    fürs Zuhören!
    Zeichnungen: Sandra Gerberding
    51
    

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52. @stgerberding
    Bonus Folien
    Zeichnungen: Sandra Gerberding
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53. @stgerberding
    HttpResponse response = HttpClient.newBuilder()
    .authenticator(new Authenticator () {
    @Override
    protected PasswordAuthentication getPasswordAuthentication() {
    return new PasswordAuthentication(
    "username",
    "password".toCharArray());
    }
    }).build()
    .send(request, HttpResponse.BodyHandlers.ofString ());
    CompletableFuture> response3 = HttpClient.newBuilder()
    .build()
    .sendAsync(request, HttpResponse.BodyHandlers.ofString());
    JDK 11 - HTTP Client
    Connection mit Authenticator
    HttpClient.newBuilder ().build ().sendAsync (request, HttpResponse.BodyHandlers.ofString ())
    .thenApply (response -> {
    System.out.println (response.statusCode ());
    return response;
    })
    .thenApply (HttpResponse::body)
    .thenAccept (System.out::println);
    Asynchronous Connection
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54. @stgerberding
    public record Cube (int height, int width, int depth) {
    }
    public final class Cube {
    private final int height;
    private final int width;
    private final int depth;
    public Cube (int height, int width, int depth) {
    this.height = height;
    this.width = width;
    this.depth = depth;
    }
    public int getHeight () {
    return height;
    }
    public int getWidth () {
    return width;
    }
    public int getDepth () {
    return depth;
    }
    @Override
    public boolean equals (Object o) {
    if (this == o) return true;
    if (o == null || getClass () != o.getClass ())
    { return false; }
    Cube cube = (Cube) o;
    return height == cube.height &&
    width == cube.width &&
    depth == cube.depth;
    }
    @Override
    public int hashCode () {
    return Objects.hash (height, width, depth);
    }
    @Override
    public String toString () {
    return "Cube {" +
    "height=" + height +
    ", width=" + width +
    ", depth=" + depth +
    '}';
    }
    }
    JDK 15 - Records Preview
    Syntax
    Struktur
    54
    

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55. @stgerberding
    public record Cube (int height, int width, int depth) implements Body {
    private final static int DENSITY = 3;
    public Cube () {
    this (1, 1, 1);
    }
    @Override
    public int volume () {
    return height () * width () * depth ();
    }
    }
    JDK 15 - Records Preview
    Syntax
    55
    

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