package cn.com.goldenwater.dcproj.utils;

import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class ListUtil {

    private static final Integer DEFAULT_MAX_SEND = 1000;

    public static <T> List<List<T>> partition(List<T> list) {
        return partition(list, DEFAULT_MAX_SEND);
    }

    public static <T> List<List<T>> partition(List<T> list, int maxSend) {
        int limit = countStep(list.size(), maxSend);
        //方法一：使用流遍历操作
//        List<List<T>> mglist = new ArrayList<>();
//        Stream.iterate(0, n -> n + 1).limit(limit).forEach(i -> {
//            mglist.add(list.stream().skip(i * maxSend).limit(maxSend).collect(Collectors.toList()));
//        });
//
//        return mglist;

        // 方法二：获取分割后的集合
        return Stream.iterate(0, n -> n + 1)
                .limit(limit)
                .parallel()
                .map(a -> list.stream()
                        .skip(a * maxSend)
                        .limit(maxSend)
                        .parallel()
                        .collect(Collectors.toList()))
                .collect(Collectors.toList());
    }

    /**
     * 计算切分次数
     */
    private static Integer countStep(Integer size, int maxSend) {
        return (size + maxSend - 1) / maxSend;
    }
}