java-8-stream-use

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.stream.IntStream;
import java.util.stream.Stream;
import java.util.function.Predicate;

public class Main{

    public static Stream<List<Integer>> getPairs(List<Integer> a, List<Integer> b){
        return a.stream().flatMap(itemA -> b.stream().map(itemB -> Arrays.asList(itemA, itemB)));
    }

    public static Stream<List<List<Integer>>> get(List<List<Integer>> dataSet) {
        return IntStream.range(0, dataSet.size()).boxed()
                .flatMap(i -> dataSet.subList(i+1, dataSet.size()).stream()
                        .map(secondry -> Arrays.asList(dataSet.get(i), secondry)));
    }

    public static void main (String[] args) {
        List<Integer> list1 = Arrays.asList(22, 23, 210, 221, 231, 236, 237, 251, 254, 278, 300, 316, 320);
        List<Integer> list2 = Arrays.asList(230);
        List<Integer> list3 = Arrays.asList(365, 366, 367, 373, 410, 413, 415, 417, 419);

        List<List<Integer>> dataset = Arrays.asList(list1, list2, list3);

        // this is the predicate
        Predicate<List<Integer>> predicate = points -> points.get(1) - points.get(0) == 1 || points.get(0) - points.get(1) == 1; 
        
        get(dataset).flatMap(datapair -> getPairs(datapair.get(0), datapair.get(1)))
                .filter(predicate).forEach(System.out::println);
  }
}