├── .gitignore
├── Java_14_Features.pdf
├── Java_15_Features.pdf
├── README.adoc
├── pom.xml
└── src
    └── main
        └── java
            └── com
                └── kodedu
                    ├── instanceofs
                        ├── InstanceOfApp1.java
                        └── InstanceOfApp2.java
                    ├── nullpointerexception
                        └── NullPointerApp.java
                    ├── records
                        ├── Point.java
                        ├── RecordsApp1.java
                        └── RecordsApp2.java
                    ├── seals
                        ├── SealedApp.java
                        └── products
                        │   ├── ConstantExpr.java
                        │   ├── Expr.java
                        │   ├── NegExpr.java
                        │   ├── PlusExpr.java
                        │   └── TimesExpr.java
                    ├── switches
                        ├── ClassicSwitchApp.java
                        ├── SwitchApp1.java
                        ├── SwitchApp2.java
                        ├── SwitchApp3.java
                        └── VehicleType.java
                    └── texts
                        ├── TextApp1.java
                        ├── TextApp2.java
                        ├── TextApp3.java
                        ├── TextApp4.java
                        ├── TextApp5.java
                        ├── TextApp6.java
                        ├── TextApp7.java
                        └── TextUtil.java


/.gitignore:
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1 | /.idea
2 | *.iml
3 | /target


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/Java_14_Features.pdf:
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https://raw.githubusercontent.com/rahmanusta/java15-edu/7ccab6d6ff36a39b396966b4d4d7f2c0398c7da7/Java_14_Features.pdf


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/Java_15_Features.pdf:
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https://raw.githubusercontent.com/rahmanusta/java15-edu/7ccab6d6ff36a39b396966b4d4d7f2c0398c7da7/Java_15_Features.pdf


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/README.adoc:
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 1 | == Java 15 Features
 2 | 
 3 | This repository includes some selected Java 15 features which have presented in conference and meetups.
 4 | 
 5 | == Notes
 6 | 
 7 | * Be sure `--enable-preview` option is enabled to run preview features
 8 | //* Be sure `-XX:+ShowCodeDetailsInExceptionMessages` option is enabled to see helpful NLP output
 9 | 
10 | == Slides
11 | 
12 | You can find slides here link:Java_15_Features.pdf[]
13 | 
14 | == How to run
15 | 
16 | Download JDK 15 https://jdk.java.net/15/ and use your favorite IDE which supports Java 14.
17 | 
18 | or you can try features on https://tryjshell.org/
19 | 
20 | == Author
21 | 
22 | Rahman Usta


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/pom.xml:
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 1 | <?xml version="1.0" encoding="UTF-8"?>
 2 | <project xmlns="http://maven.apache.org/POM/4.0.0"
 3 |          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4 |          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 5 |     <modelVersion>4.0.0</modelVersion>
 6 | 
 7 |     <groupId>com.kodedu</groupId>
 8 |     <artifactId>java15-edu</artifactId>
 9 |     <version>1.0-SNAPSHOT</version>
10 | 
11 |     <build>
12 |         <plugins>
13 |             <plugin>
14 |                 <groupId>org.apache.maven.plugins</groupId>
15 |                 <artifactId>maven-compiler-plugin</artifactId>
16 |                 <version>3.8.1</version>
17 |                 <configuration>
18 |                     <compilerArgs>
19 |                         <arg>--enable-preview</arg>
20 |                     </compilerArgs>
21 |                     <source>15</source>
22 |                     <target>15</target>
23 |                 </configuration>
24 |             </plugin>
25 |         </plugins>
26 |     </build>
27 | 
28 |     <properties>
29 |         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
30 |     </properties>
31 | 
32 | 
33 | </project>


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/src/main/java/com/kodedu/instanceofs/InstanceOfApp1.java:
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 1 | package com.kodedu.instanceofs;
 2 | 
 3 | public class InstanceOfApp1 {
 4 | 
 5 |     public static void main(String[] args) {
 6 | 
 7 |         Object obj = "Hello world!";
 8 | 
 9 |         // before
10 |         if (obj instanceof String) {
11 |             String s = (String) obj;
12 |             System.out.println("String: " + s);
13 |         }
14 | 
15 |         // after
16 |         if (obj instanceof String s) {
17 |             System.out.println("String: " + s);
18 |         }
19 |     }
20 | }
21 | 


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/src/main/java/com/kodedu/instanceofs/InstanceOfApp2.java:
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 1 | package com.kodedu.instanceofs;
 2 | 
 3 | public class InstanceOfApp2 {
 4 | 
 5 |     public static void main(String[] args) {
 6 | 
 7 |         Object obj = "Hello world!";
 8 | 
 9 |         // legal usage
10 |         if (obj instanceof String s && !s.isBlank()) {
11 |             System.out.println("String: " + s);
12 |         }
13 | 
14 |         // cannot resolve symbol 's'
15 | //        if (obj instanceof String s || !s.isBlank()) {
16 | //            System.out.println("String: " + s);
17 | //        }
18 |     }
19 | }
20 | 


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/src/main/java/com/kodedu/nullpointerexception/NullPointerApp.java:
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 1 | package com.kodedu.nullpointerexception;
 2 | 
 3 | public class NullPointerApp {
 4 | 
 5 |     /**
 6 |      * Enable flag to see helpful null pointer exception message
 7 |      * -XX:+ShowCodeDetailsInExceptionMessages
 8 |      *
 9 |      * helpful NLP is enabled by default from JDK 15
10 |      */
11 |     public static void main(String[] args) {
12 | 
13 |         Person person = new Person();
14 |         person.address = new Address();
15 |         String toUpperCase = person.address.street.toUpperCase();
16 |         System.out.println(toUpperCase);
17 | 
18 |     }
19 | 
20 |     static class Person {
21 |         Address address;
22 |     }
23 | 
24 |     static class Address {
25 |         String street;
26 |     }
27 | }
28 | 


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/src/main/java/com/kodedu/records/Point.java:
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1 | package com.kodedu.records;
2 | 
3 | public record Point(int x, int y) { }


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/src/main/java/com/kodedu/records/RecordsApp1.java:
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 1 | package com.kodedu.records;
 2 | 
 3 | public class RecordsApp1 {
 4 | 
 5 |     public static void main(String[] args) {
 6 | 
 7 |         Point point = new Point(2, 3);
 8 | 
 9 |         System.out.println(point);
10 | 
11 |         int x = point.x();
12 |         int y = point.y();
13 |         System.out.format("X: %d, Y: %d", x, y);
14 |     }
15 | }
16 | 
17 | 
18 | 


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/src/main/java/com/kodedu/records/RecordsApp2.java:
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 1 | package com.kodedu.records;
 2 | 
 3 | public class RecordsApp2 {
 4 | 
 5 |     public static void main(String[] args) {
 6 | 
 7 |         Point point1 = new Point(2, 3);
 8 |         Point point2 = new Point(2, 3);
 9 | 
10 |         System.out.println("Equal? " + point1.equals(point2));
11 |     }
12 | }
13 | 
14 | 
15 | 


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/src/main/java/com/kodedu/seals/SealedApp.java:
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 1 | package com.kodedu.seals;
 2 | 
 3 | import com.kodedu.seals.products.*;
 4 | 
 5 | public class SealedApp {
 6 | 
 7 |     public static void main(String[] args) {
 8 | 
 9 |         // y = x * 2 + 1
10 | 
11 |         var x = 3;
12 |         int y = calculate(
13 |                 new PlusExpr(
14 |                         new TimesExpr(
15 |                                 new ConstantExpr(x),
16 |                                 new ConstantExpr(2)
17 |                         ),
18 |                         new ConstantExpr(1)
19 |                 )
20 |         );
21 |         System.out.println("Value of y: " + y);
22 | 
23 |     }
24 | 
25 |     private static int calculate(Expr expr) {
26 |         if (expr instanceof ConstantExpr e) {
27 |             return e.value();
28 |         } else if (expr instanceof PlusExpr e) {
29 |             return calculate(e.first()) + calculate(e.second());
30 |         } else if (expr instanceof TimesExpr e) {
31 |             return calculate(e.first()) * calculate(e.second());
32 |         } else if (expr instanceof NegExpr e) {
33 |             return -calculate(e.expr());
34 |         } else {
35 |             throw new RuntimeException("There is no such case " + expr);
36 |         }
37 |     }
38 | }
39 | 


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/src/main/java/com/kodedu/seals/products/ConstantExpr.java:
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1 | package com.kodedu.seals.products;
2 | 
3 | public record ConstantExpr(int value) implements Expr {
4 | 
5 | }
6 | 


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/src/main/java/com/kodedu/seals/products/Expr.java:
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1 | package com.kodedu.seals.products;
2 | 
3 | public sealed interface Expr permits ConstantExpr, NegExpr, PlusExpr, TimesExpr {
4 | }
5 | 


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/src/main/java/com/kodedu/seals/products/NegExpr.java:
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1 | package com.kodedu.seals.products;
2 | 
3 | public record NegExpr(Expr expr) implements Expr {
4 | 
5 | }
6 | 


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/src/main/java/com/kodedu/seals/products/PlusExpr.java:
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1 | package com.kodedu.seals.products;
2 | 
3 | public record PlusExpr(Expr first, Expr second) implements Expr {
4 | 
5 | }
6 | 


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/src/main/java/com/kodedu/seals/products/TimesExpr.java:
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1 | package com.kodedu.seals.products;
2 | 
3 | public record TimesExpr(Expr first, Expr second) implements Expr {
4 | 
5 | }
6 | 


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/src/main/java/com/kodedu/switches/ClassicSwitchApp.java:
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 1 | package com.kodedu.switches;
 2 | 
 3 | public class ClassicSwitchApp {
 4 | 
 5 |     public static void main(String[] args) {
 6 |         VehicleType vehicleType = VehicleType.AUTOMOBILE;
 7 | 
 8 |         int speedLimit = -1;
 9 |         switch (vehicleType) {
10 |             case BIKE:
11 |             case SCOOTER:
12 |                 speedLimit = 40;
13 |                 break;
14 |             case MOTORBIKE:
15 |             case AUTOMOBILE:
16 |                 speedLimit = 140;
17 |                 break;
18 |             case TRUCK:
19 |                 speedLimit = 80;
20 |                 break;
21 |         }
22 | 
23 |         System.out.println("Speed limit: " + speedLimit);
24 |     }
25 | }
26 | 


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/src/main/java/com/kodedu/switches/SwitchApp1.java:
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 1 | package com.kodedu.switches;
 2 | 
 3 | public class SwitchApp1 {
 4 | 
 5 |     public static void main(String[] args) {
 6 | 
 7 |         VehicleType vehicleType = VehicleType.AUTOMOBILE;
 8 | 
 9 |         int speedLimit = switch (vehicleType) {
10 |             case BIKE, SCOOTER -> 40;
11 |             case MOTORBIKE, AUTOMOBILE -> 140;
12 |             case TRUCK -> 80;
13 | //            default -> throw new IllegalStateException("No case found for: " + vehicleType);
14 |         };
15 | 
16 |         System.out.println("Speed limit: " + speedLimit);
17 |     }
18 | }
19 | 


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/src/main/java/com/kodedu/switches/SwitchApp2.java:
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 1 | package com.kodedu.switches;
 2 | 
 3 | public class SwitchApp2 {
 4 | 
 5 |     public static void main(String[] args) {
 6 | 
 7 |         int speedLimit = getSpeedLimit(VehicleType.AUTOMOBILE);
 8 |         System.out.println("Speed limit: " + speedLimit);
 9 | 
10 |     }
11 | 
12 |     private static int getSpeedLimit(VehicleType vehicleType) {
13 |         return switch (vehicleType) {
14 |             case BIKE, SCOOTER -> 40;
15 |             case MOTORBIKE, AUTOMOBILE -> 140;
16 |             case TRUCK -> 80;
17 |         };
18 |     }
19 | }
20 | 


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/src/main/java/com/kodedu/switches/SwitchApp3.java:
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 1 | package com.kodedu.switches;
 2 | 
 3 | import java.util.concurrent.ThreadLocalRandom;
 4 | 
 5 | public class SwitchApp3 {
 6 | 
 7 |     public static void main(String[] args) {
 8 | 
 9 |         VehicleType vehicleType = VehicleType.TRUCK;
10 | 
11 |         int speedLimit = switch (vehicleType) {
12 |             case BIKE, SCOOTER -> 40;
13 |             case MOTORBIKE, AUTOMOBILE -> 140;
14 |             case TRUCK -> {
15 |                 int randomSpeed = ThreadLocalRandom.current().nextInt(70, 80);
16 |                 yield randomSpeed;
17 |             }
18 |         };
19 | 
20 |         System.out.println("Speed limit: " + speedLimit);
21 |     }
22 | }
23 | 


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/src/main/java/com/kodedu/switches/VehicleType.java:
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1 | package com.kodedu.switches;
2 | 
3 | public enum VehicleType {
4 |     BIKE, SCOOTER,
5 |     MOTORBIKE, AUTOMOBILE,
6 |     TRUCK
7 | }
8 | 


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/src/main/java/com/kodedu/texts/TextApp1.java:
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 1 | package com.kodedu.texts;
 2 | 
 3 | import static com.kodedu.texts.TextUtil.printText;
 4 | 
 5 | public class TextApp1 {
 6 | 
 7 |     public static void main(String[] args) {
 8 |         String html =
 9 |                 """
10 |                 <html>
11 |                     <body>
12 |                         <p>Hello, world</p>
13 |                     </body>
14 |                 </html>
15 |                 """;
16 | 
17 |         printText(html);
18 |     }
19 | }
20 | 


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/src/main/java/com/kodedu/texts/TextApp2.java:
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 1 | package com.kodedu.texts;
 2 | 
 3 | public class TextApp2 {
 4 | 
 5 |     public static void main(String[] args) {
 6 | 
 7 |         // Line  terminator is required
 8 |         // equal to-> var text = ""
 9 |         var text = """
10 |                 """;
11 | 
12 | //        var text2 = """"""; // illegal text block start
13 | //        var text3 = """ """; // illegal text block start
14 | 
15 |         TextUtil.printText(text);
16 |     }
17 | }
18 | 


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/src/main/java/com/kodedu/texts/TextApp3.java:
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 1 | package com.kodedu.texts;
 2 | 
 3 | import static com.kodedu.texts.TextUtil.printText;
 4 | 
 5 | public class TextApp3 {
 6 | 
 7 |     public static void main(String[] args) {
 8 |         String html = """
 9 |                           <html>
10 |                              <body>
11 |                                <p>Hello, world</p>
12 |                              </body>
13 |                           </html>
14 |                       """;
15 | 
16 |         printText(html);
17 |     }
18 | }
19 | 


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/src/main/java/com/kodedu/texts/TextApp4.java:
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 1 | package com.kodedu.texts;
 2 | 
 3 | import static com.kodedu.texts.TextUtil.printText;
 4 | 
 5 | public class TextApp4 {
 6 | 
 7 |     public static void main(String[] args) {
 8 |         String html = """
 9 |                           <html>
10 |                              <body>
11 |                                <p>Hello, world</p>
12 |                              </body>
13 |                           </html>
14 |                           """;
15 | 
16 |         printText(html);
17 |     }
18 | }
19 | 


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/src/main/java/com/kodedu/texts/TextApp5.java:
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 1 | package com.kodedu.texts;
 2 | 
 3 | import static com.kodedu.texts.TextUtil.printText;
 4 | 
 5 | public class TextApp5 {
 6 | 
 7 |     public static void main(String[] args) {
 8 |         String html = """
 9 |                       <html> \
10 |                          <body> \
11 |                            <p>Hello, world</p> \
12 |                          </body> \
13 |                       </html> \
14 |                       """;
15 | 
16 |         printText(html);
17 |     }
18 | }
19 | 


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/src/main/java/com/kodedu/texts/TextApp6.java:
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 1 | package com.kodedu.texts;
 2 | 
 3 | import static com.kodedu.texts.TextUtil.printText;
 4 | 
 5 | public class TextApp6 {
 6 | 
 7 |     public static void main(String[] args) {
 8 |         String html = """
 9 |                       <html>                  \s
10 |                          <body>               \s
11 |                            <p>Hello, world</p>\s
12 |                          </body>              \s
13 |                       </html>                 \s
14 |                       """;
15 |         printText(html);
16 |     }
17 | }
18 | 


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/src/main/java/com/kodedu/texts/TextApp7.java:
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 1 | package com.kodedu.texts;
 2 | 
 3 | import static com.kodedu.texts.TextUtil.printText;
 4 | 
 5 | public class TextApp7 {
 6 | 
 7 |     public static void main(String[] args) {
 8 |         String html = """
 9 |                       <html>                  
10 |                          <body>               
11 |                            <p>%s, %s</p>
12 |                          </body>              
13 |                       </html>                 
14 |                       """;
15 |         html = html.formatted("Hello", "world!");
16 | 
17 |         printText(html);
18 |     }
19 | }
20 | 


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/src/main/java/com/kodedu/texts/TextUtil.java:
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 1 | package com.kodedu.texts;
 2 | 
 3 | import java.util.concurrent.atomic.AtomicInteger;
 4 | import java.util.function.Supplier;
 5 | 
 6 | public class TextUtil {
 7 | 
 8 |     public static void printText(String string) {
 9 |         string = string.replaceAll(" ", "•");
10 |         string = string.replaceAll("\n", "⏎\n");
11 |         string = string.trim();
12 |         System.out.println(string.isBlank() ? "Blank" : string);
13 |     }
14 | 
15 | }
16 | 


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