Quick Clarifying Question about DeferredRegistries

[Syric]

From my understanding, all of my blocks, items, and whatnot should be registered like this:

    public static final RegistryObject<Block> CRASH_PAD = registry.BLOCKS.register("crash_pad", () -> new CrashPadBlock(AbstractBlock.Properties.of(Material.CLAY, MaterialColor.GRASS).friction(0.8F).sound(SoundType.SLIME_BLOCK).noOcclusion()));
    public static final RegistryObject<Item> ALCHEMICAL_FLASK = registry.ITEMS.register("alchemical_flask", () -> new Item(new Item.Properties().tab(ItemGroup.TAB_MATERIALS)));

If I then wished to refer to the crash_pad Block, or the alchemical_flask Item, do I have to refer to them as 'registry.CRASH_PAD.get()' and 'registry.ALCHEMICAL_FLASK.get()'? This seems a bit roundabout. Can I define the blocks as Blocks and the items as Items before creating and registering RegistryObject<T>s from them, or do I have to always get the blocks and items from their RegistryObjects?

[Syric]

Okay, thanks for the help! A few questions.

1. BLOCKS and ITEMS are in the same class as each other- it's called 'registry'. (forgot to capitalize, oops- I'll fix that momentarily.) What exactly shouldn't be in separate classes? Are you saying that my actual RegistryObjects (the individual blocks, items, etc.) should all be in the same class? Or that the DeferredRegisters should all be in the same class? Or that all the RegistryObject<Block>s should be in the same class as the DeferredRegister<Block>, and the RegistryObject<Item>s should be in the same class as the DeferredRegister<Item>, but those two classes don't necessarily have to be the same?
2. What is @ObjectHolder, what does it do, and where can I go to learn more? (That is, assuming it's a Forge thing. If it's a Java thing I don't know, say so and I'll go research it elsewhere- I understand and respect that this forum isn't a place to look for Java help.)

[Syric]

Understood, and I'll go check that out. Thank you so much!