Modify rule S6291[java]: Add Java examples

rules/S6291/java/rule.adoc

@@ -4,6 +4,57 @@ include::../ask-yourself.adoc[]
 
 include::../recommended.adoc[]
 
+== Sensitive Code Example
+
+For https://developer.android.com/reference/kotlin/android/database/sqlite/SQLiteDatabase[SQLiteDatabase]:
+
+----
+SQLiteDatabase db = activity.openOrCreateDatabase("test.db", Context.MODE_PRIVATE, null); // Sensitive
+----
+
+For https://developer.android.com/training/data-storage/shared-preferences[SharedPreferences]:
+
+----
+SharedPreferences pref = activity.getPreferences(Context.MODE_PRIVATE); // Sensitive
+----
+
+For https://docs.mongodb.com/realm/[Realm]:
+
+----
+RealmConfiguration config = new RealmConfiguration.Builder().build();
+Realm realm = Realm.getInstance(config); // Sensitive
+----
+
+== Compliant Solution
+
+Instead of SQLiteDatabase you can use https://www.zetetic.net/sqlcipher/sqlcipher-for-android/[SQLCipher]:
+
+----
+SQLiteDatabase db = SQLiteDatabase.openOrCreateDatabase("test.db", getKey(), null);
+----
+
+Instead of SharedPreferences you can use https://developer.android.com/reference/androidx/security/crypto/EncryptedSharedPreferences[EncryptedSharedPreferences]:
+
+----
+String masterKeyAlias = new MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC);
+EncryptedSharedPreferences.create(
+    "secret",
+    masterKeyAlias,
+    context,
+    EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
+    EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
+);
+----
+
+For Realm an encryption key can be specified in the config:
+
+----
+RealmConfiguration config = new RealmConfiguration.Builder()
+    .encryptionKey(getKey())
+    .build();
+Realm realm = Realm.getInstance(config);
+----
+
 include::../see.adoc[]
 
 
@@ -15,4 +66,4 @@ ifdef::env-github,rspecator-view[]
 
 include::../message.adoc[]
 
-endif::env-github,rspecator-view[]
+endif::env-github,rspecator-view[]