Java Practice：返回作为参数传递的相同对象

class SomeClass{
   Foo updateWithContex(Foo foo){
       foo.setAppId(i);
       foo.setXId(index);
       //.....
       return foo;
   }
}

class Foo{

    public void setAppId(int appId)
    {
       //
    }
    public void setXId(int appId)
    {
        //
    }
    public void changeState(X x)
    {
       //
    }
}

在C中,我看到过这样的代码：

BigObject&
   fastTransform( BigObject& myBO )
   {
      // When entering fastTransform(),myBO is the same object as the function
      // argument provided by the user. -> No copy-constructor is executed.
      // Transform myBO in some way
      return myBO;   // Transformed myBO is returned to the user.
   }

这也错了吗？