Java 8 toMap IllegalStateException Duplicate Key

Question

I have a file which contains data in the following format

1
2
3

I want to load this to map as {(1->1), (2->1), (3->1)}

Answer 1

The code will run if there are no duplicates in the file.

Map map1 = Files.lines(Paths.get(inputFile))
            .map(String::trim)
            .map(Integer::valueOf)
            .collect(Collectors.toMap(x -> x, x -> 1));

If there are duplicates use the following code to get the total number of occurrences in the file for that key.

Map map1 = Files.lines(Paths.get(inputFile))
            .map(String::trim)
            .map(Integer::valueOf)
            .collect(Collectors.groupingBy(x -> x, Collectors.counting());