BAEL-5682 - Atomic vs Volatile (#12528)

Co-authored-by: eugene.kovko <eugene.kovko@tensquaregames.com>

core-java-modules/core-java-concurrency-advanced-4/src/main/java/com/baeldung/atomicvsvolatile/SafeAtomicCounter.java

@@ -0,0 +1,16 @@
+package com.baeldung.atomicvsvolatile;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class SafeAtomicCounter {
+
+    private final AtomicInteger counter = new AtomicInteger(0);
+    
+    public int getValue() {
+        return counter.get();
+    }
+    
+    public void increment() {
+        counter.incrementAndGet();
+    }
+}

core-java-modules/core-java-concurrency-advanced-4/src/main/java/com/baeldung/atomicvsvolatile/UnsafeCounter.java

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+package com.baeldung.atomicvsvolatile;
+
+public class UnsafeCounter {
+
+    private int counter;
+    
+    public int getValue() {
+        return counter;
+    }
+    
+    public void increment() {
+        counter++;
+    }
+}

core-java-modules/core-java-concurrency-advanced-4/src/main/java/com/baeldung/atomicvsvolatile/UnsafeVolatileCounter.java

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+package com.baeldung.atomicvsvolatile;
+
+public class UnsafeVolatileCounter {
+
+    private volatile int counter;
+    
+    public int getValue() {
+        return counter;
+    }
+    
+    public void increment() {
+        counter++;
+    }
+}

core-java-modules/core-java-concurrency-advanced-4/src/test/java/com/baeldung/atomicvsvolatile/SafeAtomicCounterUnitTest.java

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+package com.baeldung.atomicvsvolatile;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+import org.junit.Test;
+
+public class SafeAtomicCounterUnitTest {
+
+    private static final int INCREMENT_COUNTER = 1000;
+    private static final int TIMEOUT = 100;
+    private static final int POOL_SIZE = 3;
+
+    @Test
+    public void givenMultiThread_whenSafeAtomicCounterIncrement() throws InterruptedException {
+        ExecutorService service = Executors.newFixedThreadPool(POOL_SIZE);
+        SafeAtomicCounter safeCounter = new SafeAtomicCounter();
+        IntStream.range(0, INCREMENT_COUNTER).forEach(count -> service.submit(safeCounter::increment));
+        service.awaitTermination(TIMEOUT, TimeUnit.MILLISECONDS);
+        assertEquals(INCREMENT_COUNTER, safeCounter.getValue());
+    }
+}