完成蚂蚁金服的面试题

code/src/main/java/com/raorao/java/thread/IPlusPlus.java

@@ -0,0 +1,28 @@
+package com.raorao.java.thread;
+
+/**
+ * i++ 的原子性证明.
+ *
+ * @author Xiong Raorao
+ * @since 2018-08-14-15:15
+ */
+public class IPlusPlus {
+
+  private static volatile int index = 0;
+
+  public static void main(String[] args) throws InterruptedException {
+    for (int i = 0; i < 10; i++) {
+      new Thread(() -> {
+        synchronized (IPlusPlus.class){
+          for (int j = 0; j < 10000; j++) {
+            index++;
+          }
+        }
+        System.out.println(Thread.currentThread().getName() + ", index = " + index);
+      }).start();
+    }
+    Thread.sleep(2000);
+    System.out.println(index);
+  }
+
+}