Improve AESharedItemStack caching

Reduces the item stack churn a little, improving overall server time taken from 6% to 2% on average

src/main/java/appeng/util/item/AEItemStackRegistry.java

@@ -23,14 +23,16 @@
 
 package appeng.util.item;
 
+import com.google.common.collect.MapMaker;
 import net.minecraft.item.ItemStack;
 
 import javax.annotation.Nonnull;
-import java.lang.ref.WeakReference;
-import java.util.WeakHashMap;
+import java.util.Map;
 
 public final class AEItemStackRegistry {
-    private static final WeakHashMap<AESharedItemStack, WeakReference<AESharedItemStack>> REGISTRY = new WeakHashMap<>();
+
+    private static final ItemStackHashStrategy HASH_STRATEGY = ItemStackHashStrategy.comparingAllButCount();
+    private static final Map<Integer, AESharedItemStack> REGISTRY = new MapMaker().weakValues().makeMap();
 
     private AEItemStackRegistry() {
     }
@@ -40,23 +42,18 @@ public final class AEItemStackRegistry {
             throw new IllegalArgumentException("stack cannot be empty");
         }
 
-        int oldStackSize = itemStack.getCount();
-        itemStack.setCount(1);
-
-        AESharedItemStack search = new AESharedItemStack(itemStack);
-        WeakReference<AESharedItemStack> weak = REGISTRY.get(search);
-        AESharedItemStack ret = null;
-
-        if (weak != null) {
-            ret = weak.get();
-        }
-
-        if (ret == null) {
-            ret = new AESharedItemStack(itemStack.copy());
-            REGISTRY.put(ret, new WeakReference<>(ret));
-        }
-        itemStack.setCount(oldStackSize);
-
+        var hash = HASH_STRATEGY.hashCode(itemStack);
+        var ret = REGISTRY.get(hash);
+        if (ret != null) {
             return ret;
         }
+
+        // computeIfAbsent is not feasible since new AESharedItemStack gets
+        // instantly GC'd when leaving the lambda.
+        var itemStackCopy = itemStack.copy();
+        itemStackCopy.setCount(1);
+        var sharedStack = new AESharedItemStack(itemStackCopy);
+        REGISTRY.put(hash, sharedStack);
+        return sharedStack;
+    }
 }