8269665: Clean-up toString() methods of some primitive wrappers

Reviewed-by: redestad

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

@@ -8657,6 +8657,7 @@ class Character implements java.io.Serializable, Comparable<Character>, Constabl
      *
      * @return  a string representation of this object.
      */
+    @Override
     public String toString() {
         return String.valueOf(value);
     }