add demo for ABA problem

src/main/java/threaddemo/dataracing/CASByAtomicInteger.java

@@ -0,0 +1,78 @@
+package threaddemo.dataracing;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class CASByAtomicInteger {
+    private final AtomicInteger counter = new AtomicInteger(0);
+
+    // for aba problem
+    private final AtomicInteger unSafeCounter = new AtomicInteger(0);
+
+    public static void main(String[] args) {
+        CASByAtomicInteger casByAtomicInteger = new CASByAtomicInteger();
+        casByAtomicInteger.safeIncrementDemo();
+        System.out.println("-------------------------");
+        casByAtomicInteger.unsafeIncrementDemo();
+    }
+    public void safeIncrementDemo() {
+        Thread t1 = new Thread(() -> {
+            for (int i = 0; i < 10000; i++) {
+                counter.incrementAndGet();
+            }
+        });
+        Thread t2 = new Thread(() -> {
+            for (int i = 0; i < 10000; i++) {
+                counter.incrementAndGet();
+            }
+        });
+
+        t1.start();
+        t2.start();
+        try {
+            t1.join();
+            t2.join();
+            System.out.println(STR."counter: \{counter.get()}");
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public void unsafeIncrementDemo() {
+        Thread t1 = new Thread(() -> {
+            int initValue = unSafeCounter.get();
+            System.out.println(STR."Thread 1: Initial value = \{initValue}");
+
+            unSafeCounter.compareAndSet(0,20);
+            unSafeCounter.compareAndSet(20,0);
+
+            System.out.println(STR."Thread 1: Final value = \{unSafeCounter.get()}");
+
+        },"t1");
+
+        Thread t2 = new Thread(() -> {
+            int value = unSafeCounter.get();
+            try {
+                // 等待线程1完成 ABA 操作
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            System.out.println("Thread 2: Initial value = " + value);
+
+            // 尝试 CAS 操作
+            boolean success = unSafeCounter.compareAndSet(0, 30); // A -> C
+            System.out.println(STR."Thread 2: CAS success = \{success}");
+            System.out.println(STR."Thread 2: Final value = \{unSafeCounter.get()}");
+        },"t2");
+
+        t1.start();
+        t2.start();
+
+        try {
+            t1.join();
+            t2.join();
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}