How to create the Map using Java8 Stream?

Question

How to update the Map using java 8 streams ? As for now I am doing :

        Map<String, Integer> testMap = Maps.newHashMap();

        for(Map.Entry<String,Integer> testEntrySet : testCounts.entrySet()) {
            String name = Utils.cleanName(testEntrySet.getKey());

            if(testMap.containsKey(name)) {
                testMap.put(name, testMap.get(name) +
                        testCounts.get(testEntrySet.getKey()));
            } else {
                testMap.put(name, testCounts.get(testEntrySet.getKey()));
            }

        }
        return testMap;
    }

Answer 1

I haven't tested it but I suspect your code is equivalent to:

return testCounts.entrySet().stream()
        .collect(groupingBy(e -> Utils.cleanName(e.getKey()),
                            summingInt(e -> e.getValue())));

(with the appropriate static Collectors imports).