8251203: Fix "no comment" warnings in java.base/java.lang and java/io

Reviewed-by: dfuchs, lancea, mchung, naoto

src/java.base/share/classes/java/lang/String.java

@@ -1236,6 +1236,10 @@ public final class String
      */
     public static final Comparator<String> CASE_INSENSITIVE_ORDER
                                          = new CaseInsensitiveComparator();
+
+    /**
+     * CaseInsensitiveComparator for Strings.
+     */
     private static class CaseInsensitiveComparator
             implements Comparator<String>, java.io.Serializable {
         // use serialVersionUID from JDK 1.2.2 for interoperability