# Enumerating microblock materials from Java

[API index](../API.md)

Use `MicroMaterialRegistry.materialCount()` with the existing `materialName(int)` and `getMaterial(int)` methods to
enumerate materials without importing Scala types.

## Example

The following method copies the active material names in numeric ID order:

```java
public static List<String> materialNames() {
    int count = MicroMaterialRegistry.materialCount();
    List<String> names = new ArrayList<>(count);
    for (int id = 0; id < count; id++) {
        names.add(MicroMaterialRegistry.materialName(id));
    }
    return names;
}
```

Imports and the enclosing class are in the [compiling example](../../src/test/java/codechicken/microblock/examples/MaterialEnumerationExample.java).
Use `MicroMaterialRegistry.getMaterial(id)` in the loop when you also need the `IMicroMaterial`, for example to obtain
its item. That returns the registered instance, not a copy.
The example's list is an independent copy; editing it does not change the registry.

## Timing, order and identity

- Enumerate after ForgeMicroblock has built its ID map during post-initialization. A consumer's own post-init handler
  needs suitable mod ordering if it enumerates there; later lifecycle/game callbacks can use the initialized map.
  Consumers must not call `setupIDMap()` themselves to force readiness.
- On a multiplayer client, enumeration of the connected server's IDs requires a completed, successful FMP handshake.
  FMP also rebuilds the local map before server startup. Reacquire IDs after map replacement.
- Use the game/lifecycle thread. The calls are live lookups, not an atomic snapshot: do not rebuild the map or perform
  registration/handshake work from inside an enumeration loop.
- Local setup orders IDs by material name. A multiplayer client adopts server order; do not sort or filter IDs when
  preserving a mapping. Store material names in saved data and resolve their numeric IDs for the active map.
- `materialCount()` counts ID slots, including the missing-material placeholder when present. It throws
  `IllegalStateException` before initialization and returns zero for an initialized empty map.
- A failed handshake can leave unresolved slots. The count includes them; `materialName(id)` and `getMaterial(id)`
  retain their existing `NullPointerException` for such slots. FMP disconnects the client for missing mappings.
  The count is not a handshake-success indicator, and callers should not silently skip unresolved IDs.
- The existing indexed lookups throw `ArrayIndexOutOfBoundsException` outside the active ID range and
  `NullPointerException` before map initialization.

## Migrating existing consumers

| Legacy expression | Java API |
| --- | --- |
| `getIdMap().length` | `materialCount()` |
| `getIdMap()[id]._1()` | `materialName(id)` |
| `getIdMap()[id]._2()` | `getMaterial(id)` |
| Loop over the tuple array | Loop over IDs from zero to `materialCount()`, exclusive |

For UtilitiesInExcess, apply this to `FMPRecipeLoader.run()` and `UEMultipartItem.getSubItems()`: replace each tuple
loop with an ID loop and use `materialName(id)` wherever the tuple name was used. Preserve its recipe/item ordering,
filters and material-name NBT. A material object, when needed, is available from `getMaterial(id)`.
Extra Utilities' NEI handlers use both tuple fields; both indexed replacements are available.

The static and companion `getIdMap()` methods are deprecated, with their original descriptors and live-array
behavior retained. The addition does not change packet or NBT formats.