add maven as package manager

add ShowObjectHeader.java to show object header

src/main/java/jvm/createthread/CreateByCallable.java

@@ -0,0 +1,22 @@
+package main.java.jvm.createthread;
+
+import java.util.concurrent.Callable;
+import java.util.concurrent.FutureTask;
+
+public class CreateByCallable implements Callable<String> {
+    @Override
+    public String call() throws Exception {
+        return "create by implementing Callable";
+    }
+
+    public static void main(String[] args) {
+        CreateByCallable createByCallable = new CreateByCallable();
+        FutureTask<String> futureTask = new FutureTask<>(createByCallable);
+        new Thread(futureTask).start();
+        try {
+            System.out.println(futureTask.get());
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+}