集合按规定个数分为n个部分
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第一种 (apache工具类)
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.1</version>
</dependency>
int pageSize = 5;
int pageNum = 2;
List<List<Integer>> pagedList = ListUtils.partition(originList, pageSize);
List result = null;
if(pageNum > pagedList.size()){
result = new ArrayList();
}else {
result = pagedList.get(pageNum - 1);
}
System.out.println(result);
/**
* 分页 list 数据
* @param originList
* @param pageNum
* @param pageSize
* @return
*/
public PageResult getPageByList(List<T> originList,Integer pageNum,Integer pageSize){
List<List<T>> pagedList = org.apache.commons.collections4.ListUtils.partition(originList, pageSize);
List<T> result = null;
if(pageNum > pagedList.size()){
result = new ArrayList();
}else {
result = pagedList.get(pageNum - 1);
}
return new PageResult(Long.valueOf(originList.size()),result);
}
第二种(自己封装)
package com.kakaluote.demo.utils;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* Created by 敲代码的卡卡罗特
* on 2018/12/20 12:53.
*/
public class ListUtils {
/**
* 按指定大小,分隔集合,将集合按规定个数分为n个部分
*
* @param list
* @param len
* @return
*/
public static <T> List<List<T>> splitList(List<T> list, int len) {
if (list == null || list.size() == 0 || len < 1) {
return null;
}
List<List<T>> result = new ArrayList<List<T>>();
int size = list.size();
int count = (size + len - 1) / len;
for (int i = 0; i < count; i++) {
List<T> subList = list.subList(i * len, ((i + 1) * len > size ? size : len * (i + 1)));
result.add(subList);
}
return result;
}
public static void main(String[] arg){
Timestamp a = Timestamp.valueOf("2018-05-18 09:32:32");
Timestamp b = Timestamp.valueOf("2018-05-11 09:32:32");
Timestamp c = Timestamp.valueOf("2017-05-11 09:32:32");
List<Timestamp> timestamps = Arrays.asList(a, b,c);
List<List<Timestamp>> lists = ListUtils.splitList(timestamps, 2);
System.out.println(timestamps);
}
}