Drastically reduced memory usage, mostly using deduplication.

app/com/ysoft/memory/ObjectPool.scala

@@ -0,0 +1,24 @@
+package com.ysoft.memory
+
+import java.lang.ref.{WeakReference => JWeakReference}
+import java.util
+
+class ObjectPool{
+
+  private val objects = new util.WeakHashMap[Any, JWeakReference[Any]]()//new MapMaker().concurrencyLevel(1).weakKeys().weakValues().makeMap[Any, Any]()
+
+  def apply[T](obj: T): T = synchronized{
+    // The code is intentionally low-level for performance reasons. No Option[_] used for performance reasons, no scala.ref._ wrapper is used for memory overhead reasons.
+    val res = objects.get(obj) match {
+      case null => null
+      case weakObj => weakObj.get()
+    }
+    if(res == null){
+      objects.put(obj, new JWeakReference[Any](obj))
+      obj
+    }else{
+      res.asInstanceOf[T]
+    }
+  }
+
+}