Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
//License from project: Open Source License 

import java.util.*;
import java.util.function.BiFunction;

public class Main {

    public static <T> List<T> innerJoin(List<List<T>> list, BiFunction<T, T, T> function) {
        if (list == null || function == null) {
            throw new NullPointerException("list or function must not be null");
        }
        if (list.isEmpty()) {
            return Collections.emptyList();
        }
        if (list.size() == 1) {
            return list.get(0);
        }

        List<List<T>> result = innerJoin(list.get(0), list.get(1), function);
        if (list.size() == 2) {
            return merge(result);
        } else {
            for (int i = 2; i < list.size(); i++) {
                List<T> l1 = list.get(i);
                List<List<T>> temp = new ArrayList<>();
                result.stream().forEach(l -> temp.addAll(innerJoin(l, l1, function)));
                result = temp;
            }
            return merge(result);
        }
    }

    public static <T> List<List<T>> innerJoin(List<T> l1, List<T> l2, BiFunction<T, T, T> function) {
        if (l1 == null || l2 == null) {
            throw new NullPointerException("inner join arrays must not be null");
        }

        if (l1.isEmpty() && l2.isEmpty()) {
            return Collections.emptyList();
        } else if (l1.isEmpty()) {
            return Collections.singletonList(l2);
        } else if (l2.isEmpty()) {
            return Collections.singletonList(l1);
        }

        List<List<T>> result = new ArrayList<>(l1.size() * l2.size());
        l1.stream().forEach(t1 -> {
            List<T> l = new ArrayList<>();
            l2.stream().forEach(t2 -> l.add(function.apply(t1, t2)));
            result.add(l);
        });
        return result;
    }

    public static <T> List<T> merge(List<List<T>> list) {
        List<T> result = new ArrayList<>();
        list.stream().forEach(result::addAll);
        return result;
    }
}