Java 8 partition list

Question

Is it possible to partition a List in pure Jdk8 into equal chunks (sublists).

I know it is possible using Guava Lists class, but can we do it with pure Jdk? I don\'t wan

Answer 1

I have tried my own solution with a custom made Collector. I hope someone will find it useful, or help me improve it.

class PartitioningCollector implements Collector>, List>> {

        private final int batchSize;
        private final List batch;

        public PartitioningCollector(int batchSize) {
            this.batchSize = batchSize;
            this.batch = new ArrayList<>(batchSize);
        }

        @Override
        public Supplier>> supplier() {
            return LinkedList::new;
        }

        @Override
        public BiConsumer>, T> accumulator() {
            return (total, element) -> {
                batch.add(element);
                if (batch.size() >= batchSize) {
                    total.add(new ArrayList<>(batch));
                    batch.clear();
                }
            };
        }

        @Override
        public BinaryOperator>> combiner() {
            return (left, right) -> {
                List> result = new ArrayList<>();
                result.addAll(left);
                result.addAll(left);
                return result;
            };
        }

        @Override
        public Function>, List>> finisher() {
            return result -> {
                if (!batch.isEmpty()) {
                    result.add(new ArrayList<>(batch));
                    batch.clear();
                }
                return result;
            };
        }

        @Override
        public Set characteristics() {
            return emptySet();
        }
    }