SimplifyCollector

Reports collectors that can be simplified.

In particular, some cascaded groupingBy() collectors can be expressed by using a simpler toMap() collector, which is also likely to be more performant.

Example:

Collectors.groupingByConcurrent(String::length, Collectors.collectingAndThen(Collectors.maxBy(String::compareTo), Optional::get));

After the quick-fix is applied:

Collectors.toConcurrentMap(String::length, Function.identity(), BinaryOperator.maxBy(String::compareTo));

New in 2017.1