JEP 488: Primitive Types in Patterns, instanceof, and switch (Second Preview)

Author: ibrahimatay

java-24/pom.xml

@@ -16,5 +16,18 @@
         <maven.compiler.target>24</maven.compiler.target>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>24</source>
+                    <target>24</target>
+                    <compilerArgs>--enable-preview</compilerArgs>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
 
 </project>

java-24/src/main/java/JEP488PrimitiveTypesInPatternsInstanceofAndSwitch.java

@@ -0,0 +1,61 @@
+import java.util.Map;
+
+public class JEP488PrimitiveTypesInPatternsInstanceofAndSwitch {
+    public static void main(String[] args) {
+        // JEP 488: Primitive Types in Patterns, instanceof, and switch (Second Preview)
+        // https://openjdk.org/jeps/488
+
+        // Primitive Types ile Pattern Matching
+        Object obj = 42;
+        if (obj instanceof int i) {
+            System.out.printf("Primitive int value: %1$s\n", i);
+        }
+
+        // Switch for Primitive Type
+        System.out.printf("%1$s HTTP status code refers to a %2$s%n", 100, getHTTPCodeDesc(100));
+        System.out.printf("%1$s HTTP status code refers to a %2$s%n", 200, getHTTPCodeDesc(200));
+        System.out.printf("%1$s HTTP status code refers to a %2$s%n", 403, getHTTPCodeDesc(403));
+        System.out.printf("%1$s HTTP status code refers to a %2$s%n", 0, getHTTPCodeDesc(0));
+
+        // Record Patterns with Primitive Types
+        JsonValue json = new JsonObject(Map.of(
+                "name", new JsonString("Alice"),
+                "age", new JsonNumber(28)
+        ));
+
+        if (json instanceof JsonObject(var map)
+                && map.get("name") instanceof JsonString(var name)
+                && map.get("age") instanceof JsonNumber(var age)) {
+            System.out.printf("Name: %s, Age: %.0f%n", name, age);
+        }
+    }
+
+    // Switch for Primitive Type
+    public static String getHTTPCodeDesc(int code){
+        return switch(code) {
+            case 100 -> "Continue";
+            case 200 -> "OK";
+            case 301 -> "Moved Permanently";
+            case 302 -> "Found";
+            case 400 -> "Bad Request";
+            case 500 -> "Internal Server Error";
+            case 502 -> "Bad Gateway";
+            case int i when (i > 100 && i < 200) -> "Informational";
+            case int i when (i > 200 && i < 300) -> "Successful";
+            case int i when (i > 302 && i < 400) -> "Redirection";
+            case int i when (i > 400 && i < 500) -> "Client Error";
+            case int i when (i > 502 && i < 600) -> "Server Error";
+            default -> "Unknown error";
+        };
+    }
+}
+
+interface Human {}
+class Employee implements Human {}
+class Boss implements Human {}
+
+sealed interface JsonValue permits JsonString, JsonNumber, JsonObject {}
+
+record JsonString(String value) implements JsonValue {}
+record JsonNumber(double value) implements JsonValue {}
+record JsonObject(Map<String, JsonValue> map) implements JsonValue {}