Merge pull request #296 from jinyahuan/juc-atomic-jyh

Add usage demos

docs/java/Multithread/Atomic.md

@@ -268,7 +268,121 @@ class Person {
 Daisy
 20
 ```
+#### 4.3 AtomicStampedReference 类使用示例
 
+```java
+import java.util.concurrent.atomic.AtomicStampedReference;
+
+public class AtomicStampedReferenceDemo {
+    public static void main(String[] args) {
+        // 实例化、取当前值和 stamp 值
+        final Integer initialRef = 0, initialStamp = 0;
+        final AtomicStampedReference<Integer> asr = new AtomicStampedReference<>(initialRef, initialStamp);
+        System.out.println("currentValue=" + asr.getReference() + ", currentStamp=" + asr.getStamp());
+
+        // compare and set
+        final Integer newReference = 666, newStamp = 999;
+        final boolean casResult = asr.compareAndSet(initialRef, newReference, initialStamp, newStamp);
+        System.out.println("currentValue=" + asr.getReference()
+                + ", currentStamp=" + asr.getStamp()
+                + ", casResult=" + casResult);
+
+        // 获取当前的值和当前的 stamp 值
+        int[] arr = new int[1];
+        final Integer currentValue = asr.get(arr);
+        final int currentStamp = arr[0];
+        System.out.println("currentValue=" + currentValue + ", currentStamp=" + currentStamp);
+
+        // 单独设置 stamp 值
+        final boolean attemptStampResult = asr.attemptStamp(newReference, 88);
+        System.out.println("currentValue=" + asr.getReference()
+                + ", currentStamp=" + asr.getStamp()
+                + ", attemptStampResult=" + attemptStampResult);
+
+        // 重新设置当前值和 stamp 值
+        asr.set(initialRef, initialStamp);
+        System.out.println("currentValue=" + asr.getReference() + ", currentStamp=" + asr.getStamp());
+
+        // [不推荐使用，除非搞清楚注释的意思了] weak compare and set
+        // 困惑！weakCompareAndSet 这个方法最终还是调用 compareAndSet 方法。[版本: jdk-8u191]
+        // 但是注释上写着 "May fail spuriously and does not provide ordering guarantees,
+        // so is only rarely an appropriate alternative to compareAndSet."
+        // todo 感觉有可能是 jvm 通过方法名在 native 方法里面做了转发
+        final boolean wCasResult = asr.weakCompareAndSet(initialRef, newReference, initialStamp, newStamp);
+        System.out.println("currentValue=" + asr.getReference()
+                + ", currentStamp=" + asr.getStamp()
+                + ", wCasResult=" + wCasResult);
+    }
+}
+```
+
+输出结果如下：
+```
+currentValue=0, currentStamp=0
+currentValue=666, currentStamp=999, casResult=true
+currentValue=666, currentStamp=999
+currentValue=666, currentStamp=88, attemptStampResult=true
+currentValue=0, currentStamp=0
+currentValue=666, currentStamp=999, wCasResult=true
+```
+
+#### 4.4 AtomicStampedReference 类使用示例
+
+``` java
+import java.util.concurrent.atomic.AtomicMarkableReference;
+
+public class AtomicMarkableReferenceDemo {
+    public static void main(String[] args) {
+        // 实例化、取当前值和 mark 值
+        final Boolean initialRef = null, initialMark = false;
+        final AtomicMarkableReference<Boolean> amr = new AtomicMarkableReference<>(initialRef, initialMark);
+        System.out.println("currentValue=" + amr.getReference() + ", currentMark=" + amr.isMarked());
+
+        // compare and set
+        final Boolean newReference1 = true, newMark1 = true;
+        final boolean casResult = amr.compareAndSet(initialRef, newReference1, initialMark, newMark1);
+        System.out.println("currentValue=" + amr.getReference()
+                + ", currentMark=" + amr.isMarked()
+                + ", casResult=" + casResult);
+
+        // 获取当前的值和当前的 mark 值
+        boolean[] arr = new boolean[1];
+        final Boolean currentValue = amr.get(arr);
+        final boolean currentMark = arr[0];
+        System.out.println("currentValue=" + currentValue + ", currentMark=" + currentMark);
+
+        // 单独设置 mark 值
+        final boolean attemptMarkResult = amr.attemptMark(newReference1, false);
+        System.out.println("currentValue=" + amr.getReference()
+                + ", currentMark=" + amr.isMarked()
+                + ", attemptMarkResult=" + attemptMarkResult);
+
+        // 重新设置当前值和 mark 值
+        amr.set(initialRef, initialMark);
+        System.out.println("currentValue=" + amr.getReference() + ", currentMark=" + amr.isMarked());
+
+        // [不推荐使用，除非搞清楚注释的意思了] weak compare and set
+        // 困惑！weakCompareAndSet 这个方法最终还是调用 compareAndSet 方法。[版本: jdk-8u191]
+        // 但是注释上写着 "May fail spuriously and does not provide ordering guarantees,
+        // so is only rarely an appropriate alternative to compareAndSet."
+        // todo 感觉有可能是 jvm 通过方法名在 native 方法里面做了转发
+        final boolean wCasResult = amr.weakCompareAndSet(initialRef, newReference1, initialMark, newMark1);
+        System.out.println("currentValue=" + amr.getReference()
+                + ", currentMark=" + amr.isMarked()
+                + ", wCasResult=" + wCasResult);
+    }
+}
+```
+
+输出结果如下：
+```
+currentValue=null, currentMark=false
+currentValue=true, currentMark=true, casResult=true
+currentValue=true, currentMark=true
+currentValue=true, currentMark=false, attemptMarkResult=true
+currentValue=null, currentMark=false
+currentValue=true, currentMark=true, wCasResult=true
+```
 
 ### 5 对象的属性修改类型原子类