android: Convert BiMap to Kotlin

src/android/app/src/main/java/org/yuzu/yuzu_emu/utils/BiMap.java

@@ -1,22 +0,0 @@
-package org.yuzu.yuzu_emu.utils;
-
-import java.util.HashMap;
-import java.util.Map;
-
-public class BiMap<K, V> {
-    private Map<K, V> forward = new HashMap<K, V>();
-    private Map<V, K> backward = new HashMap<V, K>();
-
-    public synchronized void add(K key, V value) {
-        forward.put(key, value);
-        backward.put(value, key);
-    }
-
-    public synchronized V getForward(K key) {
-        return forward.get(key);
-    }
-
-    public synchronized K getBackward(V key) {
-        return backward.get(key);
-    }
-}

src/android/app/src/main/java/org/yuzu/yuzu_emu/utils/BiMap.kt

@@ -0,0 +1,22 @@
+package org.yuzu.yuzu_emu.utils
+
+class BiMap<K, V> {
+    private val forward: MutableMap<K, V> = HashMap()
+    private val backward: MutableMap<V, K> = HashMap()
+
+    @Synchronized
+    fun add(key: K, value: V) {
+        forward[key] = value
+        backward[value] = key
+    }
+
+    @Synchronized
+    fun getForward(key: K): V? {
+        return forward[key]
+    }
+
+    @Synchronized
+    fun getBackward(key: V): K? {
+        return backward[key]
+    }
+}