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.st.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;
}
}
java stream
@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 -> CateLevel() == 2)
.map((province) -> {
// 针对单个省设置⼦级地区
province.setChildren(getChildrens(province, allArea));
return province;
}).sorted((province1, province2) -> {
Sort() - Sort();
}).List());
// 打印结果
System.out.println("areaList:" + JSONString(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 -> CatId() == ParentCid())
// 嵌套，递归查下⼀级地区
.map((area) -> {
area.setChildren(getChildrens(area, allArea));
return area;
// 排序
}).sorted((area1, area2) -> {
Sort() - Sort();
}).List());
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);

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