树形数据结构的处理

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.serializer.SerializerFeature;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

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

/**
 * @Classname TreeTest
 * @Description 树 结构的拼装
 * @Date 2020/11/8 12:14
 * @Author zhangjiahao
 */
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class TreeTest {
    private Integer keyId;
    private Integer parentId;
    private String name;
    private List<TreeTest> children ;

    private static Integer count =0 ;
    public static void main(String[] args) {
        List<TreeTest> initList = init();
        //找出根父节点
        List<TreeTest> topNode = initList.stream().filter(p -> p.getParentId() == 0).collect(Collectors.toList());
        //找出叶子节点
        List<TreeTest> childrenNode = initList.stream().filter(p -> p.getParentId() != 0).collect(Collectors.toList());
        //递归执行
        findChild(childrenNode,topNode);
        //输出时间复杂度
        System.out.println(count);
        //输出结果   fastJson做解析器如果对象有重复会出现循环调用  显示出对象地址，加入序列化解决
        System.out.println(JSON.toJSONString(builder().keyId(0).children(topNode).build(), SerializerFeature.DisableCircularReferenceDetect));
    }
    private static void findChild(List<TreeTest>childrenNode ,List<TreeTest> topNode){
        //遍历根节点
        topNode.forEach(p->{
            //筛选如果子节点的parentId与父节点的id相等  则进入if分支
            if(childrenNode.stream().anyMatch(t->t.getParentId().equals(p.getKeyId()))){
                //筛选出当前父节点的儿子节点
                List<TreeTest> collect = childrenNode.stream().filter(t -> t.getParentId().equals(p.getKeyId())).collect(Collectors.toList());
                //计算时间复杂度
                count++;
                //为当前父节点添加儿子
                collect.forEach(p.getChildren()::add);
            }
            //将当前的父节点的儿子节点  递归调用：其中，子节点还是所有子节点，当前父节点的儿子节点进入寻找子节点
            findChild(childrenNode,p.getChildren());
        });
    }


    private static List<TreeTest> init (){
        List<TreeTest> allTree = new ArrayList<>(1);
        TreeTest zjh = builder().keyId(1).name("zjh").parentId(0).children(new ArrayList<>()).build();
        TreeTest fwh = builder().keyId(2).name("fwh").parentId(0).children(new ArrayList<>()).build();
        TreeTest zzh = builder().keyId(3).name("zzh").parentId(0).children(new ArrayList<>()).build();

        TreeTest zjh1 = builder().keyId(4).name("zjh2").parentId(1).children(new ArrayList<>()).build();
        TreeTest fwh1 = builder().keyId(5).name("fwh2").parentId(2).children(new ArrayList<>()).build();
        TreeTest zzh1 = builder().keyId(6).name("zzh2").parentId(3).children(new ArrayList<>()).build();

        TreeTest zjh2 = builder().keyId(7).name("zjh3").parentId(4).children(new ArrayList<>()).build();
        TreeTest fwh2 = builder().keyId(8).name("fwh3").parentId(5).children(new ArrayList<>()).build();
        TreeTest fwh3 = builder().keyId(10).name("fwh3.1").parentId(5).children(new ArrayList<>()).build();
        TreeTest zzh2 = builder().keyId(9).name("zzh3").parentId(6).children(new ArrayList<>()).build();

        allTree.add(zjh);
        allTree.add(zjh1);
        allTree.add(zjh2);

        allTree.add(fwh);
        allTree.add(fwh1);
        allTree.add(fwh2);
        allTree.add(fwh3);

        allTree.add(zzh);
        allTree.add(zzh1);
        allTree.add(zzh2);
        return allTree;
    }
}