Added support for serializing Pairs

src/main/java/world/bentobox/bentobox/database/json/BentoboxTypeAdapterFactory.java

@@ -1,5 +1,7 @@
 package world.bentobox.bentobox.database.json;
 
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
 import java.util.Map;
 
 import org.bukkit.Location;
@@ -25,9 +27,11 @@
 import world.bentobox.bentobox.database.json.adapters.ItemStackTypeAdapter;
 import world.bentobox.bentobox.database.json.adapters.LocationTypeAdapter;
 import world.bentobox.bentobox.database.json.adapters.MaterialTypeAdapter;
+import world.bentobox.bentobox.database.json.adapters.PairTypeAdapter;
 import world.bentobox.bentobox.database.json.adapters.PotionEffectTypeAdapter;
 import world.bentobox.bentobox.database.json.adapters.VectorTypeAdapter;
 import world.bentobox.bentobox.database.json.adapters.WorldTypeAdapter;
+import world.bentobox.bentobox.util.Pair;
 
 
 /**
@@ -74,6 +78,13 @@ public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
             return (TypeAdapter<T>) new WorldTypeAdapter();
         } else if (Vector.class.isAssignableFrom(rawType)) {
             return (TypeAdapter<T>) new VectorTypeAdapter();
+        } else if (Pair.class.isAssignableFrom(rawType)) {
+            // Add Pair handling here with type safety
+            Type pairType = type.getType();
+            ParameterizedType parameterizedType = (ParameterizedType) pairType;
+            Type xType = parameterizedType.getActualTypeArguments()[0];
+            Type zType = parameterizedType.getActualTypeArguments()[1];
+            return (TypeAdapter<T>) new PairTypeAdapter<>(xType, zType);
         } else if (ConfigurationSerializable.class.isAssignableFrom(rawType)) {
             // This covers a lot of Bukkit objects
             return (TypeAdapter<T>) new BukkitObjectTypeAdapter(gson.getAdapter(Map.class));

src/main/java/world/bentobox/bentobox/database/json/adapters/PairTypeAdapter.java

@@ -0,0 +1,50 @@
+package world.bentobox.bentobox.database.json.adapters;
+
+import java.io.IOException;
+import java.lang.reflect.Type;
+
+import com.google.gson.Gson;
+import com.google.gson.TypeAdapter;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+
+import world.bentobox.bentobox.util.Pair;
+
+public class PairTypeAdapter<X, Z> extends TypeAdapter<Pair<X, Z>> {
+    private final Type xType;
+    private final Type zType;
+
+    public PairTypeAdapter(Type xType, Type zType) {
+        this.xType = xType;
+        this.zType = zType;
+    }
+
+    @Override
+    public void write(JsonWriter out, Pair<X, Z> pair) throws IOException {
+        out.beginObject();
+        out.name("x");
+        Gson gson = new Gson();
+        gson.toJson(pair.getKey(), xType, out);
+        out.name("z");
+        gson.toJson(pair.getValue(), zType, out);
+        out.endObject();
+    }
+
+    @Override
+    public Pair<X, Z> read(JsonReader in) throws IOException {
+        X x = null;
+        Z z = null;
+
+        in.beginObject();
+        while (in.hasNext()) {
+            String name = in.nextName();
+            if (name.equals("x")) {
+                x = new Gson().fromJson(in, xType);
+            } else if (name.equals("z")) {
+                z = new Gson().fromJson(in, zType);
+            }
+        }
+        in.endObject();
+        return new Pair<>(x, z);
+    }
+}