将一个List均分为n份2021-10-23

import com.alibaba.fastjson.JSON;
import org.springframework.util.CollectionUtils;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class AverageAssign {

    public static <T> List<List<T>> averageAssign(List<T> source, int listCount) {
        if (listCount <= 0 || CollectionUtils.isEmpty(source)) {
            return Collections.emptyList();
        }
        List<List<T>> result = new ArrayList<>();
        if (source.size() < listCount) {
            result.add(source);
            return result;
        }
        // 先计算出余数
        int remainder = source.size() % listCount;
        // 然后是商
        int number = source.size() / listCount;
        // 偏移量
        int offset = 0;

        for (int i = 0; i < listCount; i++) {
            List<T> value;
            // 剩余可以分成remainder份
            if (remainder > 0) {
                value = source.subList(i * number + offset, (i + 1) * number + offset + 1);
                /**
                 * remainder、offset如果要变，得是同样的step，比如remainder-=2，offset+=2
                */
                remainder--;
                offset++;
            } else {
                value = source.subList(i * number + offset, (i + 1) * number + offset);
            }
            result.add(value);
        }
        return result;
    }

    public static void main(String[] args) {
        List<String> list = new ArrayList<String>();
        list.add("ni");
        list.add("hao");
        list.add("an");
        list.add("yu");
        list.add("ge");
        list.add("happy");
        list.add("year");
        list.add("hi");
        list.add("hi");
        List<List<String>> lists = AverageAssign.averageAssign(list, 4);
        System.out.println(JSON.toJSONString(lists));
    }
}