大集合拆分成多个小集合

1. 场景

在数据库批量操作时，有可能数据量过大，不能一次性操作，所以需要将大集合拆分为多个小集合进行多次操作

2. 拆分集合方法（写了三种）

import com.google.common.collect.Lists;
import com.xin.demo.fastjsondemo.FastJsonFormatPrintUtils;
import org.apache.commons.collections4.CollectionUtils;import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;public class PartitionListDemo {private static final int PARTITION_SIZE = 10;public static void main(String[] args) {// 大集合List<String> list = new ArrayList<>();for (int i = 0; i < 33; i++) {list.add("xinliushijian" + i);}// 方法1 guava工具List<List<String>> partitionList = Lists.partition(list, PARTITION_SIZE);FastJsonFormatPrintUtils.formatPrint(partitionList);System.out.println("===============");// 方法2 stream流实现List<List<String>> partitionList1 = partList1(list, PARTITION_SIZE);FastJsonFormatPrintUtils.formatPrint(partitionList1);// 方法3 普通方法实现partList2(list, PARTITION_SIZE);}public static <T> List<List<T>> partList1(List<T> list, int size) {if (CollectionUtils.isEmpty(list) || size < 1) {return new ArrayList<>();}List<List<T>> partList = IntStream.range(0, list.size()).boxed().collect(Collectors.groupingBy(index -> index / size)).values().stream().map(indices -> indices.stream().map(list::get).collect(Collectors.toList())).collect(Collectors.toList());return partList;}public static <T> List<List<T>> partList2(List<T> list, int size) {if (CollectionUtils.isEmpty(list) || size < 1) {return new ArrayList<>();}List<List<T>> allPartList = new ArrayList<>();for (int i = 0; i < list.size(); i+=size) {if (i + size > list.size()) {size  = list.size() - i;}List<T> parList = list.subList(i, i + size);allPartList.add(parList);}FastJsonFormatPrintUtils.formatPrint(allPartList);return allPartList;}}

3. 格式化打印方法

import com.alibaba.fastjson.serializer.SerializerFeature;
import com.alibaba.fastjson.JSON;public class FastJsonFormatPrintUtils {public static void formatPrint(Object object) {String pretty = JSON.toJSONString(object, SerializerFeature.PrettyFormat, SerializerFeature.WriteMapNullValue,SerializerFeature.WriteDateUseDateFormat);System.out.println(pretty);}}