本文内容

• 手动对List内元素进行分页处理
• 对分页查询有个更立体的认识

前置知识

• 三目运算
• 集合
• eclipse/My eclipse/IDEA 工具

环境

· JDK 1.8

具体源码

实体类

public class Paging {
    private Integer totalNum;
    private Integer totalPage;
    private Integer pageSize;
    private Integer pageIndex;
    private Integer queryIndex;

    public Paging subPaging(Integer totalNum, Integer pageSize, Integer pageIndex) {
        Paging page = new Paging();
        page.setTotalNum(totalNum);
        Integer totalPage = totalNum % pageSize == 0 ? totalNum / pageSize : totalNum / pageSize + 1;
        page.setTotalPage(totalPage);
        page.setPageIndex(pageIndex + 1);
        page.setPageSize(pageSize);
        page.setQueryIndex(pageSize * pageIndex);
        return page;

    }

    public Integer getTotalNum() {
        return totalNum;
    }

    public void setTotalNum(Integer totalNum) {
        this.totalNum = totalNum;
    }

    public Integer getTotalPage() {
        return totalPage;
    }

    public void setTotalPage(Integer totalPage) {
        this.totalPage = totalPage;
    }

    public Integer getPageSize() {
        return pageSize;
    }

    public void setPageSize(Integer pageSize) {
        this.pageSize = pageSize;
    }

    public Integer getPageIndex() {
        return pageIndex;
    }

    public void setPageIndex(Integer pageIndex) {
        this.pageIndex = pageIndex;
    }

    public Integer getQueryIndex() {
        return queryIndex;
    }

    public void setQueryIndex(Integer queryIndex) {
        this.queryIndex = queryIndex;
    }

}

测试类

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

public class testPaging {
    public static void main(String[] args) {
        List<String> list = test();
        for (String string : list) {
            System.out.println(string);
        }
    }

    public static List<String> test() {
        List<String> strs = new ArrayList<String>();
        String str1 = "1";
        String str2 = "2";
        String str3 = "3";
        String str4 = "4";
        String str5 = "5";
        String str6 = "6";
        String str7 = "7";
        String str8 = "8";
        String str9 = "9";
        String str10 = "10";
        strs.add(str1);
        strs.add(str2);
        strs.add(str3);
        strs.add(str4);
        strs.add(str5);
        strs.add(str6);
        strs.add(str7);
        strs.add(str8);
        strs.add(str9);
        strs.add(str10);
        int totalNum = strs.size();
        int pageSize = 3;
        int pageIndex = 0;
        Paging paging = new Paging().subPaging(totalNum, pageSize, pageIndex);
        int fromIndex = paging.getQueryIndex();
        int totalIndex = 0;
        if (fromIndex + paging.getPageIndex() >= totalNum) {
            totalIndex = totalNum;
        } else {
            totalIndex = fromIndex + paging.getPageSize();
        }
        if (fromIndex > totalIndex) {
            return Collections.emptyList();
        }
        return strs.subList(fromIndex, totalIndex);

    }
}

以下为测试结果：

        int totalNum = strs.size();
        int pageSize = 3;
        int pageIndex = 0;

测试结果1

        int totalNum = strs.size();
        int pageSize = 3;
        int pageIndex = 1;

测试结果2

        int totalNum = strs.size();
        int pageSize = 5;
        int pageIndex = 1;

测试结果3