BIP39: Japanese word separator

app/src/main/java/eu/faircode/email/BIP39.java

@@ -1,6 +1,7 @@
 package eu.faircode.email;
 
 import android.content.Context;
+import android.text.TextUtils;
 
 import androidx.annotation.NonNull;
 
@@ -9,12 +10,23 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.security.SecureRandom;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Locale;
 
 public class BIP39 {
     // https://github.com/bitcoin/bips/tree/master/bip-0039
     // https://github.com/bitcoin/bips/pull/1129
-    static String getWord(@NonNull Locale locale, int index, Context context) {
+    static String getMnemonic(@NonNull Locale locale, int words, Context context) {
+        List<String> list = new ArrayList<>();
+        SecureRandom rnd = new SecureRandom();
+        for (int i = 0; i < words; i++)
+            list.add(BIP39.getWord(locale, rnd.nextInt(2048), context));
+        String delimiter = ("ja".equals(locale.getLanguage()) ? "\u3000" : " ");
+        return TextUtils.join(delimiter, list);
+    }
+
+    private static String getWord(@NonNull Locale locale, int index, Context context) {
         String lang = locale.getLanguage();
         if ("zh".equals(lang) && "CN".equals(locale.getCountry()))
             lang = "zh_cn";

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

@@ -58,12 +58,8 @@ import androidx.preference.PreferenceManager;
 import androidx.webkit.WebViewFeature;
 
 import java.io.IOException;
-import java.nio.ByteBuffer;
-import java.security.SecureRandom;
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
-import java.util.ArrayList;
-import java.util.List;
 import java.util.Locale;
 
 public class FragmentOptionsPrivacy extends FragmentBase implements SharedPreferences.OnSharedPreferenceChangeListener {
@@ -466,13 +462,7 @@ public class FragmentOptionsPrivacy extends FragmentBase implements SharedPrefer
             public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
                 if (checked) {
                     Context context = compoundButton.getContext();
-
-                    Locale locale = Locale.getDefault();
-                    List<String> words = new ArrayList<>();
-                    SecureRandom rnd = new SecureRandom();
-                    for (int i = 0; i < BIP39_WORDS; i++)
-                        words.add(BIP39.getWord(locale, rnd.nextInt(2048), context));
-                    String mnemonic = TextUtils.join(" ", words);
+                    String mnemonic = BIP39.getMnemonic(Locale.getDefault(), BIP39_WORDS, context);
 
                     prefs.edit().putString("wipe_mnemonic", mnemonic).apply();
                     tvMnemonic.setText(mnemonic);