BAEL-7778 - A Guide to @locked in Lombok (#17765)

* BAEL-7778 - A Guide to @locked in Lombok

* Update java version

Author: apeterlic

lombok-modules/lombok-3/pom.xml

@@ -34,4 +34,9 @@
         </plugins>
     </build>
 
+    <properties>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
+    </properties>
+
 </project>

lombok-modules/lombok-3/src/main/java/com/baeldung/lombok/locked/Counter.java

@@ -0,0 +1,18 @@
+package com.baeldung.lombok.locked;
+
+import lombok.Locked;
+
+public class Counter {
+
+    private int counter = 0;
+
+    @Locked.Write
+    public void increment() {
+        counter++;
+    }
+
+    @Locked.Read
+    public int get() {
+        return counter;
+    }
+}

lombok-modules/lombok-3/src/test/java/com/baeldung/lombok/locked/CounterUnitTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.lombok.locked;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class CounterUnitTest {
+
+    @Test
+    void givenCounter_whenIncrementCalledMultipleTimes_thenReturnCorrectResult() throws InterruptedException {
+        Counter counter = new Counter();
+
+        Thread.Builder builder = Thread.ofVirtual()
+            .name("worker-", 0);
+        Runnable task = counter::increment;
+
+        Thread t1 = builder.start(task);
+        t1.join();
+
+        Thread t2 = builder.start(task);
+        t2.join();
+
+        assertEquals(2, counter.get());
+    }
+}