@Testpublic void test14() throws Exception { Map<String, Integer> m1 = ImmutableMap.of("a", 2, "b", 3); Map<String, Integer> m2 = ImmutableMap.of("a", 3, "c", 4); Map<String, Integer> mx = Stream.of(m1, m2) .map(Map::entrySet) // converts each map into an entry set .flatMap(Collection::stream) // converts each set into an entry stream, then // "concatenates" it in place of the original set .collect( Collectors.toMap( // collects into a map Map.Entry::getKey, // where each entry is based Map.Entry::getValue, // on the entries in the stream Integer::max // such that if a value already exist for // a given key, the max of the old // and new value is taken ) ) ; Map<String, Integer> expected = ImmutableMap.of("a", 3, "b", 3, "c", 4); assertEquals(expected, mx);}
