/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception {
		List<Integer> l = Arrays.asList(1,2,3,4,5,5,6,6,7,7,7,8,3,8,8);
		final int N=3;
		System.out.println(nSizeParts(l,N));
		System.out.println(nTimeParts(l,N));
	}
		private static <T> List<List<T>> nSizeParts(List<T> objs, final int N) {
		return new ArrayList<>(IntStream.range(0, objs.size()).boxed().collect(
				Collectors.groupingBy(e->e/N,Collectors.mapping(e->objs.get(e), Collectors.toList())
						)).values());
	}
		private static <T> List<List<T>> nTimeParts(List<T> objs, final int N) {
		return new ArrayList<>(IntStream.range(0, objs.size()).boxed().collect(
				Collectors.groupingBy(e->e%N,Collectors.mapping(e->objs.get(e), Collectors.toList())
						)).values());
	}
}

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