src/java.base/share/classes/java/util/Comparators.java

*** 64,73 ****
--- 64,74 ----
      static final class NullComparator<T> implements Comparator<T>, Serializable {
          @java.io.Serial
          private static final long serialVersionUID = -7569533591570686392L;
          private final boolean nullFirst;
          // if null, non-null Ts are considered equal
+         @SuppressWarnings("serial") // Not statically typed as Serializable
          private final Comparator<T> real;
  
          @SuppressWarnings("unchecked")
          NullComparator(boolean nullFirst, Comparator<? super T> real) {
              this.nullFirst = nullFirst;