JEP 409: Sealed Classes

Author: ibrahimatay

README.md

@@ -10,6 +10,9 @@ This repository contains Java examples that are designed to track and document t
   * [JEP 431](https://openjdk.org/jeps/431): Sequenced Collections
   * [JEP 444](https://openjdk.org/jeps/444): Virtual Threads
 
+* [Java 17](java-17/) (September, 2021)
+  * [JEP 409](https://openjdk.org/jeps/409): Sealed Classes
+
 * [Java 16](java-16/) (March, 2021)
   * [JEP 395](https://openjdk.java.net/jeps/395): Records
 

java-17/pom.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<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">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>com.ibrahimatay</groupId>
+        <artifactId>Java-Features</artifactId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>java-17</artifactId>
+
+    <properties>
+        <maven.compiler.source>17</maven.compiler.source>
+        <maven.compiler.target>17</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>

java-17/src/main/java/com/ibrahimatay/JEP409SealedClasses.java

@@ -0,0 +1,54 @@
+package com.ibrahimatay;
+
+/*
+
+JEP 409: Sealed Classes
+https://openjdk.org/jeps/409
+ */
+
+import java.util.UUID;
+
+public class JEP409SealedClasses {
+    public static void main(String[] args) {
+        System.out.println(getNumberOfSeats(new Truck(100, UUID.randomUUID().toString())));
+        System.out.println(getNumberOfSeats(new Car(20, UUID.randomUUID().toString())));
+    }
+
+    static int getNumberOfSeats(Vehicle vehicle) {
+        if (vehicle instanceof Car) {
+            return ((Car) vehicle).getNumberOfSeats();
+        } else if (vehicle instanceof Truck) {
+            return ((Truck) vehicle).getLoadCapacity();
+        } else {
+            throw new RuntimeException("Unknown instance of Vehicle");
+        }
+    }
+}
+
+sealed interface Vehicle permits Car, Truck {
+    String getRegistrationNumber();
+}
+
+record Car(int numberOfSeats, String registrationNumber) implements Vehicle {
+
+    @Override
+    public String getRegistrationNumber() {
+        return registrationNumber;
+    }
+
+    public int getNumberOfSeats() {
+        return numberOfSeats;
+    }
+}
+
+record Truck(int loadCapacity, String registrationNumber) implements Vehicle {
+
+    @Override
+    public String getRegistrationNumber() {
+        return registrationNumber;
+    }
+
+    public int getLoadCapacity() {
+        return loadCapacity;
+    }
+}

pom.xml

@@ -18,6 +18,7 @@
         <module>java-6</module>
         <module>java-16</module>
         <module>java-21</module>
+        <module>java-17</module>
     </modules>
 
     <properties>