优化代码，改正 Javadoc。

src/test/java/xyz/zhouxy/plusone/commons/util/SimpleJdbcTemplateTests.java

@@ -27,7 +27,7 @@ class SimpleJdbcTemplateTests {
 
     private static final Logger log = LoggerFactory.getLogger(SimpleJdbcTemplateTests.class);
 
-    DataSource dataSource;
+    final DataSource dataSource;
 
     String[] cStruct = {
             "id",

src/test/java/xyz/zhouxy/plusone/commons/util/TreeBuilderTests.java

@@ -31,7 +31,7 @@ class TreeBuilderTests {
                 MenuItem.of("C", "C2", "二级菜单C2", "/c/c2"),
                 MenuItem.of("C", "C3", "二级菜单C3", "/c/c3")
         );
-        List<Menu> menuTree = new TreeBuilder<Menu, String>(
+        List<Menu> menuTree = new TreeBuilder<>(
                 menus,
                 Menu::getMenuCode,
                 Menu::getParentMenuCode,