JAVA List和Map切割工具详解

import org.springframework.util.CollectionUtils;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

import java.util.Set;

/**

  * @author lanfangyi

  * @version 1.0

  * @since 2019/2/28 20:39

  */

public class CollectionUtil {

   private CollectionUtil(){

   }

   /**

    * 将map切成段，作用与PHP的array_chunk函数相当

    *

    * @param chunkMap 被切段的map

    * @param chunkNum 每段的大小

    * @param <k>   map的key类型

    * @param <v>   map的value类型 如果是自定义类型，则必须实现equals和hashCode方法

    * @return

    */

   public static <k, v> List<Map<k, v>> mapChunk(Map<k, v> chunkMap, int chunkNum) {

     if (chunkMap == null || chunkNum <= 0 ) {

       List<Map<k, v>> list = new ArrayList<>();

       list.add(chunkMap);

       return list;

     }

     Set<k> keySet = chunkMap.keySet();

     Iterator<k> iterator = keySet.iterator();

     int i = 1 ;

     List<Map<k, v>> total = new ArrayList<>();

     Map<k, v> tem = new HashMap<>();

     while (iterator.hasNext()) {

       k next = iterator.next();

       tem.put(next, chunkMap.get(next));

       if (i == chunkNum) {

         total.add(tem);

         tem = new HashMap<>();

         i = 0 ;

       }

       i++;

     }

     if (!CollectionUtils.isEmpty(tem)){

       total.add(tem);

     }

     return total;

   }

   /**

    * 将list切割

    *

    * @param chunkList 被分隔的数组

    * @param chunkNum 每段的大小

    * @param <T>    List中的类型

    * @return

    */

   public static <T> List<List<T>> listChunk(List<T> chunkList, int chunkNum) {

     if (chunkList == null || chunkNum <= 0 ) {

       List<List<T>> t = new ArrayList<>();

       t.add(chunkList);

       return t;

     }

     Iterator<T> iterator = chunkList.iterator();

     int i = 1 ;

     List<List<T>> total = new ArrayList<>();

     List<T> tem = new ArrayList<>();

     while (iterator.hasNext()) {

       T next = iterator.next();

       tem.add(next);

       if (i == chunkNum) {

         total.add(tem);

         tem = new ArrayList<>();

         i = 0 ;

       }

       i++;

     }

     if (!CollectionUtils.isEmpty(tem)){

       total.add(tem);

     }

     return total;

   }

}

List<Map<String,Object>> listMap = new ArrayList<>();

Map<String,Object> map = new HashMap<String,Object>();

List<Entity> list = new ArrayList<>();

map.put( "list" ,list);

listMap.add(map);