Sums { public static ReduceByKey.CombineFunctionWithIdentity<Integer> ofInts() { return SUMS_OF_INT; } private  Sums(); static ReduceByKey.CombineFunctionWithIdentity<Long> ofLongs(); static ReduceByKey.CombineFunctionWithIdentity<Integer> ofInts(); static ReduceByKey.CombineFunctionWithIdentity<Float> ofFloats(); static ReduceByKey.CombineFunctionWithIdentity<Double> ofDoubles();  }
@Test public void testSumOfInts() { assertEquals(6, (int) apply(Stream.of(1, 2, 3), Sums.ofInts())); }