Meh.java

    public static void main(String[] args)
    {
        final Map<String, List<String>> map = new HashMap<>();

        map.put("foo", Arrays.asList("bar", "baz"));
        map.put("foo2", Arrays.asList("bar2", "baz2"));

        map.entrySet().stream().flatMap(e -> {
            final Stream.Builder<Map.Entry<String, String>> builder
                = Stream.builder();
            final String k = e.getKey();
            e.getValue().stream().forEach(v -> builder.accept(new AbstractMap
                .SimpleEntry<>(k, v)));
            return builder.build();
        }).forEach(System.out::println);
    }