Added classifier version

app/src/main/java/eu/faircode/email/MessageClassifier.java

@@ -48,6 +48,7 @@ import javax.mail.Address;
 import javax.mail.internet.InternetAddress;
 
 public class MessageClassifier {
+    private static int version = 3;
     private static boolean loaded = false;
     private static boolean dirty = false;
     private static final Map<Long, List<String>> accountMsgIds = new HashMap<>();
@@ -425,7 +426,8 @@ public class MessageClassifier {
         try (JsonWriter writer = new JsonWriter(new BufferedWriter(new FileWriter(file)))) {
             writer.beginObject();
 
-            writer.name("version").value(2);
+            Log.i("Classifier write version=" + version);
+            writer.name("version").value(version);
 
             writer.name("messages");
             writer.beginArray();
@@ -517,13 +519,15 @@ public class MessageClassifier {
     private static synchronized void _load(File file) throws IOException {
         Log.i("Classifier read " + file);
         long start = new Date().getTime();
+        version = 0;
         if (file.exists())
             try (JsonReader reader = new JsonReader(new BufferedReader(new FileReader(file)))) {
                 reader.beginObject();
                 while (reader.hasNext())
                     switch (reader.nextName()) {
                         case "version":
-                            reader.nextInt();
+                            version = reader.nextInt();
+                            Log.i("Classifier read version=" + version);
                             break;
 
                         case "messages":
@@ -684,7 +688,7 @@ public class MessageClassifier {
                         Log.i("Classifier dropping account=" + account +
                                 " word=" + word + " class=" + clazz + " freq=" + freq.count + " avg=" + avg);
                         wordClassFrequency.get(account).get(word).remove(clazz);
-                    } else if (false) {
+                    } else if (version >= 3) {
                         for (String b : new ArrayList<>(freq.before.keySet()))
                             if (freq.before.get(b) < freq.count / 20)
                                 freq.before.remove(b);