To Find Highest Frequency number with the frequency following code can be use quite nicely
@Test
public void findHighestFrequency() throws Exception {
Stream.of(1,2,2,1,2,1,2,2,1,2,1,2,2,1,2,1,2,2,1,2,1,2,2,1,2)
.collect(Collectors.groupingBy(Function.identity(), Collectors.counting()))
.entrySet().stream()
.max((a,b) -> a.getValue().compareTo(b.getValue()))
.ifPresent(System.out::println);
}