create MaterialSet$Singleton class

common/api/src/main/java/com/dfsek/terra/api/util/collection/MaterialSet.java

@@ -9,7 +9,14 @@ package com.dfsek.terra.api.util.collection;
 
 import java.io.Serial;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashSet;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.Objects;
+import java.util.Spliterator;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
 
 import com.dfsek.terra.api.block.BlockType;
 import com.dfsek.terra.api.block.state.BlockState;
@@ -20,9 +27,7 @@ public class MaterialSet extends HashSet<BlockType> {
     private static final long serialVersionUID = 3056512763631017301L;
     
     public static MaterialSet singleton(BlockType material) {
-        MaterialSet set = new MaterialSet();
-        set.add(material);
-        return set;
+        return new Singleton(material);
     }
     
     public static MaterialSet get(BlockType... materials) {
@@ -44,4 +49,108 @@ public class MaterialSet extends HashSet<BlockType> {
     private void add(BlockState data) {
         add(data.getBlockType());
     }
+    
+    private static final class Singleton extends MaterialSet {
+        private final BlockType element;
+        
+        Singleton(BlockType e) {
+            element = e;
+        }
+        
+        public Iterator<BlockType> iterator() {
+            return new Iterator<>() {
+                private boolean hasNext = true;
+                
+                public boolean hasNext() {
+                    return hasNext;
+                }
+                
+                public BlockType next() {
+                    if(hasNext) {
+                        hasNext = false;
+                        return element;
+                    }
+                    throw new NoSuchElementException();
+                }
+                
+                public void remove() {
+                    throw new UnsupportedOperationException();
+                }
+                
+                @Override
+                public void forEachRemaining(Consumer<? super BlockType> action) {
+                    Objects.requireNonNull(action);
+                    if(hasNext) {
+                        hasNext = false;
+                        action.accept(element);
+                    }
+                }
+            };
+        }
+        
+        public int size() {
+            return 1;
+        }
+        
+        public boolean contains(Object o) {
+            return Objects.equals(o, element);
+        }
+        
+        // Override default methods for Collection
+        @Override
+        public void forEach(Consumer<? super BlockType> action) {
+            action.accept(element);
+        }
+        
+        @Override
+        public Spliterator<BlockType> spliterator() {
+            return new Spliterator<>() {
+                long est = 1;
+                
+                @Override
+                public Spliterator<BlockType> trySplit() {
+                    return null;
+                }
+                
+                @Override
+                public boolean tryAdvance(Consumer<? super BlockType> consumer) {
+                    Objects.requireNonNull(consumer);
+                    if(est > 0) {
+                        est--;
+                        consumer.accept(element);
+                        return true;
+                    }
+                    return false;
+                }
+                
+                @Override
+                public void forEachRemaining(Consumer<? super BlockType> consumer) {
+                    tryAdvance(consumer);
+                }
+                
+                @Override
+                public long estimateSize() {
+                    return est;
+                }
+                
+                @Override
+                public int characteristics() {
+                    int value = (element != null) ? Spliterator.NONNULL : 0;
+                    
+                    return value | Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.IMMUTABLE |
+                           Spliterator.DISTINCT | Spliterator.ORDERED;
+                }
+            };
+        }
+        
+        @Override
+        public boolean removeIf(Predicate<? super BlockType> filter) {
+            throw new UnsupportedOperationException();
+        }
+        
+        @Override
+        public int hashCode() {
+            return Objects.hashCode(element);
+        }
+    }
 }

common/implementation/base/src/main/java/com/dfsek/terra/config/loaders/MaterialSetLoader.java

@@ -36,6 +36,11 @@ public class MaterialSetLoader implements TypeLoader<MaterialSet> {
     @Override
     public MaterialSet load(@NotNull AnnotatedType type, @NotNull Object o, @NotNull ConfigLoader configLoader, DepthTracker depthTracker) throws LoadException {
         List<String> stringData = (List<String>) o;
+        
+        if(stringData.size() == 1) {
+            return MaterialSet.singleton(configLoader.loadType(BlockType.class, stringData.get(0), depthTracker));
+        }
+        
         MaterialSet set = new MaterialSet();
         
         for(String string : stringData) {