Tutorial/Docs in-memory off-heap

[Pro100AlexHell]

Please make a tutorial and docs: how to create in-memory (off-heap) objects, how to allocate, how to serialize/deserialize (if need, i can't understand) this to byte array (located off-heap), how to change it fields.
For example now (in current system) I have class
User
{
long Id;
List[ItemA] ItemsA; // class ItemA { .. }
List[ItemB] ItemsB; // class ItemB { .. }
// and many more field
}

// and global collection
static HashMap[long, User] AllUsers;

// .. dynamically created users, dynamically filled ItemsA, B, ..

as I understand, I need use SharedMemoryMap.java or subclasses, but can't understend how.
and how to allocate new User, it's new ItemA, how to put, get to User.ItemsA collection.

is it enough to replace my static HashMap[long, User] AllUsers into SharedMemoryMap[long, User] or not?

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should I see https://github.com/odnoklassniki/shared-memory-cache ? can't understand where is the full cache/allocate code.