Change Permutation Filter (#598)

Co-authored-by: slprime <history-21@yandex.ru>

src/main/java/codechicken/nei/ItemStackMap.java

@@ -9,6 +9,7 @@ import java.util.LinkedHashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Function;
 
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
@@ -222,6 +223,19 @@ public class ItemStackMap<T> {
         map.put(key, value);
     }
 
+    public T computeIfAbsent(ItemStack key, Function<ItemStack, ? extends T> mappingFunction) {
+        T value;
+        if ((value = get(key)) == null) {
+            T newValue;
+            if ((newValue = mappingFunction.apply(key)) != null) {
+                put(key, newValue);
+                return newValue;
+            }
+        }
+
+        return value;
+    }
+
     public void clear() {
         itemMap.clear();
         size = 0;