8.【原创】使用Java8中的Stream特性筛选数据

package com.fatsea.gulimall.product;

import com.alibaba.fastjson.JSON;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

@SpringBootTest
class GulimallProductApplicationTests
{

    class Area {
        // 地区编号
        private Integer catId;
        // 地区名称
        private String name;
        // 地区父ID
        private Integer parentCid;
        // 地区等级：2-省、3-市、4-区县、5-街道
        private Integer cateLevel;
        // 地区排序值：越小越靠前
        private Integer sort;
        // 子地区
        List<Area> children;

        public Area() {
        }

        public Area(Integer catId, String name, Integer parentCid,Integer sort, Integer cateLevel) {
            this.catId = catId;
            this.name = name;
            this.parentCid = parentCid;
            this.sort = sort;
            this.cateLevel = cateLevel;
        }

        public Integer getCatId() {
            return catId;
        }

        public void setCatId(Integer catId) {
            this.catId = catId;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public Integer getParentCid() {
            return parentCid;
        }

        public void setParentCid(Integer parentCid) {
            this.parentCid = parentCid;
        }

        public Integer getCateLevel() {
            return cateLevel;
        }

        public void setCateLevel(Integer cateLevel) {
            this.cateLevel = cateLevel;
        }

        public Integer getSort() {
            return sort;
        }

        public void setSort(Integer sort) {
            this.sort = sort;
        }

        public List<Area> getChildren() {
            return children;
        }

        public void setChildren(List<Area> children) {
            this.children = children;
        }
    }

    @Test
    void testDataFilter ()
    {
        // 准备数据
        List<Area> allArea = new ArrayList<>();
        allArea.add(new Area(1, "江西",0, 14, 2));
        allArea.add(new Area(2, "湖北",0, 13, 2));
        allArea.add(new Area(3, "湖南",0, 12, 2));
        allArea.add(new Area(4, "九江",1, 11, 3));
        allArea.add(new Area(5, "南昌",1, 10, 3));
        allArea.add(new Area(6, "景德镇",1, 9, 3));
        allArea.add(new Area(7, "浮梁",6, 8, 3));
        allArea.add(new Area(8, "昌江",6, 7, 3));
        allArea.add(new Area(9, "乐平",6, 6, 3));
        allArea.add(new Area(10, "东湖区",5, 5, 4));
        allArea.add(new Area(11, "南昌县",5, 4, 4));
        allArea.add(new Area(12, "新建县",5, 3, 4));
        allArea.add(new Area(13, "柴桑区",4, 2, 4));
        allArea.add(new Area(14, "塔山街道",9, 1, 5));

        // 筛选出省级地区:并排序
        List<Area> provinceList = allArea.stream()
                .filter(area -> area.getCateLevel() == 2)
                .map((province) -> {
                    // 针对单个省设置子级地区
                    province.setChildren(getChildrens(province, allArea));
                    return province;
                }).sorted((province1, province2) -> {
                    return province1.getSort() - province2.getSort();
                }).collect(Collectors.toList());

        // 打印结果
        System.out.println("areaList:" + JSON.toJSONString(provinceList));
        /*[
            {"catId":3,"cateLevel":2,"name":"湖南","parentCid":0,"sort":12,"children":[]},
            {"catId":2,"cateLevel":2,"name":"湖北","parentCid":0,"sort":13,"children":[]},
            {"catId":1,"cateLevel":2,"name":"江西","parentCid":0,"sort":14,"children":
                [
                    {"catId":6,"cateLevel":3,"name":"景德镇","parentCid":1,"sort":9,"children":
                        [
                            {"catId":9,"cateLevel":3,"name":"乐平","parentCid":6,"sort":6,"children":
                                    [
                                        {"catId":14,"cateLevel":5,"children":[],"name":"塔山街道","parentCid":9,"sort":1}
                                    ]
                            },
                            {"catId":8,"cateLevel":3,"children":[],"name":"昌江","parentCid":6,"sort":7},
                            {"catId":7,"cateLevel":3,"children":[],"name":"浮梁","parentCid":6,"sort":8}
                        ]
                    },
                    {"catId":5,"cateLevel":3,"name":"南昌","parentCid":1,"sort":10,"children":
                        [
                            {"catId":12,"cateLevel":4,"name":"新建县","parentCid":5,"sort":3,"children":[]},
                            {"catId":11,"cateLevel":4,"name":"南昌县","parentCid":5,"sort":4,"children":[]},
                            {"catId":10,"cateLevel":4,"name":"东湖区","parentCid":5,"sort":5,"children":[]}
                        ]
                    },
                    {"catId":4,"cateLevel":3,"name":"九江","parentCid":1,"sort":11,"children":
                        [
                            {"catId":13,"cateLevel":4,"name":"柴桑区","parentCid":4,"sort":2,"children":[]}
                        ]
                    }
                ]
            }
        ]*/
    }

    // 递归筛选每个省级地区的子级
    public List<Area> getChildrens (Area root, List<Area> allArea) {
        // 筛选子级
        List<Area> children = allArea.stream()
                // 筛选出当前地区的下一级
                .filter(area -> root.getCatId() == area.getParentCid())
                // 嵌套，递归查找下一级地区
                .map((area) -> {
                    area.setChildren(getChildrens(area, allArea));
                    return area;
                // 排序
                }).sorted((area1, area2) -> {
                    return area1.getSort() - area2.getSort();
                }).collect(Collectors.toList());
        return children;
    }
}

同样的数据采用js的方式筛选：

　　

var arr = [
    { catId: 1, name: "江西", parentCid: 0, cateLevel: 2 },
    { catId: 2, name: "湖北", parentCid: 0, cateLevel: 2 },
    { catId: 3, name: "湖南", parentCid: 0, cateLevel: 2 },
    { catId: 4, name: "九江", parentCid: 1, cateLevel: 3 },
    { catId: 5, name: "南昌", parentCid: 1, cateLevel: 3 },
    { catId: 6, name: "景德镇", parentCid: 1, cateLevel: 3 },
    { catId: 7, name: "浮梁", parentCid: 6, cateLevel: 4 },
    { catId: 8, name: "昌江", parentCid: 6, cateLevel: 4 },
    { catId: 9, name: "乐平", parentCid: 6, cateLevel: 4 },
    { catId: 10, name: "东湖区", parentCid: 5, cateLevel: 4 },
    { catId: 11, name: "南昌县", parentCid: 5, cateLevel: 4 },
    { catId: 12, name: "新建县", parentCid: 5, cateLevel: 4 },
    { catId: 13, name: "柴桑区", parentCid: 4, cateLevel: 4 },
    { catId: 14, name: "塔山街道", parentCid: 9, cateLevel: 5 }
];

arr.sort(function(a, b) {
    return b.cateLevel - a.cateLevel;
});

console.log('arr = ', arr);

var obj1 = {};
var rs_arr = [];

for(var i=0; i<arr.length; i++)
{
    var data = arr[i];
    var cid = data.catId;
    var pid = data.parentCid;
    var lev = data.cateLevel;

    data.child = obj1[cid] ? obj1[cid] : [];
    
    if(obj1[pid])
    {
        obj1[pid].push(data);
    }
    else
    {
        obj1[pid] = [data];
    }
    
    if(2 == lev)
    {
        rs_arr.push(data)
    }
}

rs_arr.sort(function(a, b) {
    return a.catId - b.catId;
});

console.log('rs_arr = ', rs_arr);