Some mistakes you’d avoid in java

With great power comes great responsibilities.

Lambda

Map vs ForEach

Please noted map won’t execute code inside. If you want to make it invoked for each item, please replace it with forEach.

Lets assume one quesiont, which finding intersections of a list of arrays.

public int[] intersectionOfArray(List<int[]> input) {
        List<Integer> list = new ArrayList<>();
        Map<Integer, Integer> map = new HashMap<>();
        Consumer<? super int[]> processRow=row-> Arrays.stream(row).forEach(it->map.put(it,map.getOrDefault(it,0)+1));
        input.forEach(processRow);
        Predicate<? super Map.Entry<Integer, Integer>> filterSize=entry->entry.getValue()==input.size();
        final int[] array = map.entrySet().stream().filter(filterSize).map(Map.Entry::getKey).mapToInt(i -> i).toArray();
        return array;
    }

Please be advised following line won’t work if you replace forEach with map.

Consumer<? super int[]> processRow=row-> Arrays.stream(row).forEach(it->map.put(it,map.getOrDefault(it,0)+1));

Above Function to be used in following

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