Slice a stream into batches (Java)

Sliced.java

import java.util.*;
import java.util.stream.Stream;

public final class StreamUtils {
    public static <A> Stream<List<A>> sliced(final Stream<A> stm, final int sliceSize){
        final ArrayList<A> lst = new ArrayList<>(sliceSize);
        final int[] cnt = {0};
        final Stream<ArrayList<A>> sliced = stm.flatMap(el -> {
            if (cnt[0] == sliceSize) {
                cnt[0] = 0;
                ArrayList<A> batch = new ArrayList<>(lst);
                lst.clear();
                return Stream.of(batch);
            } else {
                cnt[0] += 1;
                lst.add(el);
                return Stream.empty();
            }
        });
        return Stream.concat(sliced, Stream.generate(() -> lst));
    }
}

Why are you using an int[] rather than, say, an AtomicInteger?