Fix condition, add documentation

src/main/java/net/minestom/server/inventory/FillOption.java

@@ -8,11 +8,21 @@ import java.util.Map;
 @FunctionalInterface
 public interface FillOption<T> {
 
+    /**
+     * Place as much as the item as possible.
+     * <p>
+     * The remaining, can be air.
+     */
     FillOption<ItemStack> ALL = (inventory, result, itemChangesMap) -> {
         itemChangesMap.forEach(inventory::safeItemInsert);
         return result;
     };
 
+    /**
+     * Only place the item if can be fully added.
+     * <p>
+     * Returns true if the item has been added, false if nothing changed.
+     */
     FillOption<Boolean> ALL_OR_NOTHING = (inventory, result, itemChangesMap) -> {
         if (result.isAir()) {
             // Item can be fully placed inside the inventory, do so
@@ -24,7 +34,12 @@ public interface FillOption<T> {
         }
     };
 
-    FillOption<Boolean> DRY_RUN = (inventory, result, itemChangesMap) -> !result.isAir();
+    /**
+     * Loop through the inventory items without changing anything.
+     * <p>
+     * Returns true if the item can be fully added, false otherwise.
+     */
+    FillOption<Boolean> DRY_RUN = (inventory, result, itemChangesMap) -> result.isAir();
 
     T fill(@NotNull AbstractInventory inventory,
            @NotNull ItemStack result,

src/main/java/net/minestom/server/thread/ThreadProvider.java

@@ -38,7 +38,7 @@ public abstract class ThreadProvider {
 
     {
         // Default thread count in the pool (cores * 2)
-        setThreadCount(NettyRuntime.availableProcessors() * 2);
+        setThreadCount(1);
     }
 
     /**