Add some Java 22 new features

Signed-off-by: Manoel Campos <manoelcampos@gmail.com>

.github/workflows/maven.yml

@@ -16,10 +16,10 @@ jobs:
 
     steps:
     - uses: actions/checkout@v3
-    - name: Set up JDK 20
+    - name: Set up JDK 22
       uses: actions/setup-java@v3
       with:
-        java-version: '20'
+        java-version: '22'
         distribution: 'zulu'
         cache: maven
     - name: Build with Maven

README.adoc

@@ -19,3 +19,4 @@ https://gitpod.io/#https://github.com/manoelcampos/jdk-new-features[image:https:
 - link:src/main/java/samples/jdk17/Jdk17.java[JDK 17 Examples]
 - link:src/main/java/samples/jdk18/Jdk18.java[JDK 18 Examples]
 - link:src/main/java/samples/jdk19/Jdk19.java[JDK 19 Examples]
+- link:src/main/java/samples/jdk22/Jdk22.java[JDK 22 Examples]

pom.xml

@@ -19,7 +19,7 @@
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.8.1</version>
                 <configuration>
-                    <release>20</release>
+                    <release>22</release>
                     <compilerArgs>
                         <arg>--enable-preview</arg>
                     </compilerArgs>

src/main/java/samples/jdk22/Jdk22.java

@@ -0,0 +1,76 @@
+package samples.jdk22;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+
+class SampleClass{
+    private final String jdkVersion;
+
+    SampleClass(final String jdkVersion) {
+        this.jdkVersion = Objects.requireNonNull(jdkVersion);
+    }
+
+    public String getJdkVersion() {
+        return jdkVersion;
+    }
+}
+
+public class Jdk22 extends SampleClass {
+    /**
+     * Instance main method. A simplified version of the main method that can be used in a class,
+     * which doesn't require to be static and don't need a String array if you aren't going
+     * to take command line parameters.
+     * @see <a href="https://openjdk.org/jeps/463"></a>
+     */
+    void main() {
+        new Jdk22();
+    }
+
+    /**
+     * A constructor showing how to use statements before calling the super constructor.
+     * @see <a href="https://openjdk.org/jeps/447">https://openjdk.org/jeps/447</a>
+     */
+    public Jdk22(){
+        // Calling any statements before a super or this construtor was not allowed before.
+        unamedVar();
+        stringTemplate();
+        super("JDK 22");
+    }
+
+    /**
+     * Shows how to use string template with the new {@link StringTemplate#STR} processor,
+     * so that you can interpolate variables directly into a string,
+     * following the pattern: {@snippet : STR."My message here: \{variableX}"}
+     *
+     * You don't need to import the {@link StringTemplate} class to use it.
+     * The processor is automatically available in the classpath as if it was directly inside java.lang package.
+     *
+     * @see <a href="https://openjdk.org/jeps/459">https://openjdk.org/jeps/459</a>
+     */
+    private static void stringTemplate(){
+        final String name = "Manoel";
+        final int age = 44;
+        final String role = "Software Engineer";
+        final String msg = STR."Hello, my name is \{name}, I'm \{age} years old and I'm a \{role}.";
+        System.out.println(msg);
+    }
+
+    /**
+     * Shows how to use underscore to represent an unused variable/parameter,
+     * so that it is ignored and can't be used.
+     * @see <a href="https://openjdk.java.net/jeps/456">https://openjdk.java.net/jeps/456</a>
+     */
+    private static void unamedVar(){
+        //Heights initially in centimeters
+        final var personHeightMap = new HashMap<>(
+                Map.of("John", 180.0, "Mary", 160.0, "Peter", 175.0, "Lucy", 165.0, "Paul", 190.0, "Alice", 155.0,
+                       "Mark", 170.0, "Sandra", 175.0, "David", 185.0, "Eva", 160.0));
+
+        // Converts the heights to meters
+        // The name key is not being used in the lambda expression, so it can be replaced by an underscore
+        personHeightMap.replaceAll((_, height) -> height/100.0);
+        personHeightMap.forEach((name, height) -> System.out.printf("Name: %s | Height %.2fm\n", name, height));
+        System.out.println();
+    }
+}