Fix minor checkstyle issues

- Add JavaDoc where checkstyle expects it
- Fix line too long issues
- ...

src/main/java/fr/xephi/authme/datasource/DataSourceResult.java

@@ -3,7 +3,7 @@ package fr.xephi.authme.datasource;
 /**
  * Wraps a value and allows to specify whether a value is missing or the player is not registered.
  */
-public class DataSourceResult<T> {
+public final class DataSourceResult<T> {
 
     /** Instance used when a player does not exist. */
     private static final DataSourceResult UNKNOWN_PLAYER = new DataSourceResult<>(null);

src/main/java/fr/xephi/authme/datasource/MySQL.java

@@ -89,6 +89,11 @@ public class MySQL implements DataSource {
         setParameters(settings);
     }
 
+    /**
+     * Retrieves various settings.
+     *
+     * @param settings the settings to read properties from
+     */
     private void setParameters(Settings settings) {
         this.host = settings.getProperty(DatabaseSettings.MYSQL_HOST);
         this.port = settings.getProperty(DatabaseSettings.MYSQL_PORT);
@@ -112,6 +117,9 @@ public class MySQL implements DataSource {
         this.useSsl = settings.getProperty(DatabaseSettings.MYSQL_USE_SSL);
     }
 
+    /**
+     * Sets up the connection arguments to the database.
+     */
     private void setConnectionArguments() {
         ds = new HikariDataSource();
         ds.setPoolName("AuthMeMYSQLPool");
@@ -159,6 +167,9 @@ public class MySQL implements DataSource {
         return ds.getConnection();
     }
 
+    /**
+     * Creates the table or any of its required columns if they don't exist.
+     */
     private void checkTablesAndColumns() throws SQLException {
         try (Connection con = getConnection(); Statement st = con.createStatement()) {
             // Create table with ID column if it doesn't exist

src/main/java/fr/xephi/authme/datasource/converter/VAuthConverter.java

@@ -42,8 +42,9 @@ public class VAuthConverter implements Converter {
                     } catch (Exception | NoSuchMethodError e) {
                         pname = getName(UUID.fromString(name));
                     }
-                    if (pname == null)
+                    if (pname == null) {
                         continue;
+                    }
                     auth = PlayerAuth.builder()
                         .name(pname.toLowerCase())
                         .realName(pname)