Introduction to methods of List segmentation operation in Java

This article mainly introduces relevant information about examples of List segmentation operations in Java. I hope that through this article, everyone can master the method of implementing list segmentation. Friends who need it can refer to it

Examples of List segmentation operations in java

Question: Suppose system A queries a very large List, and now system B wants to get this list to export reports, but system B’s deployment environment Conditions are limited and the memory cannot accommodate such a large List. At this time, we need to split the List and export it one by one.

If we follow the traditional method, it may be more cumbersome. We can use the subList method in List to achieve it. The code is as follows:

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

public class listTest {

  public static void main(String[] args) {
    List<String> list = new ArrayList<String>();
    list.add("aaa");//index_0
    list.add("bbb");//index_1
    list.add("ccc");//index_2
    list.add("ddd");//index_3
    list.add("eee");//index_4
    list.add("fff");//index_5
    list.add("ggg");//index_6

    int flag = 3;//每次取的数据

    int size = list.size();
    int temp = size / flag + 1;
    boolean special = size % flag == 0;
    List<String> cutList = null;
    for (int i = 0; i < temp; i++) {
      if (i == temp - 1) {
        if (special) {
          break;
        }
        cutList = list.subList(flag * i, size);
      } else {
        cutList = list.subList(flag * i, flag * (i + 1));
      }
      System.out.println("第" + (i + 1) + "组：" + cutList.toString());
    }
  }
}

Test:

1, flag = 1

##

第1组：[aaa]
第2组：[bbb]
第3组：[ccc]
第4组：[ddd]
第5组：[eee]
第6组：[fff]
第7组：[ggg]

2, flag = 2

##

第1组：[aaa, bbb]
第2组：[ccc, ddd]
第3组：[eee, fff]
第4组：[ggg]

3, flag = 10

第1组：[aaa, bbb, ccc, ddd, eee, fff, ggg]

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