java 递归写树

1、创建实体类

@Getter
@Setter
public class Muem {
    private Integer id;
    private Integer parentId;
    private String name;
    List<Muem> child;

    public Muem (Integer id,Integer parentId,String name){
        this.id = id;
        this.parentId = parentId;
        this.name = name;
    }

    public Muem (){
    }

2、递归方法类

public class MenuTree {

    private List<Muem> menuList = new ArrayList<Muem>();
      public MenuTree(List<Muem> menuList) {
                 this.menuList=menuList;
            }
	
    public List<Muem> getParents(List<Muem> muems){
        List<Muem> tree = new LinkedList<>();
        Iterator<Muem> iterator = muems.iterator();
        while (iterator.hasNext()){
            Muem muem = iterator.next();
            //获取最上层根
            if (muem.getParentId() ==null || muem.getParentId().equals(0)){
                Muem child = new Muem();
                BeanUtils.copyProperties(muem,child);
                tree.add(child);
                iterator.remove();
            }
        }
        //递归写树
        this.recursion(tree,muems);
        return tree;
    }

    public void recursion(List<Muem> tree,List<Muem> muems){
        for (Muem t : tree){
            Iterator<Muem> iterator = muems.iterator();
            while (iterator.hasNext()){
                Muem muem = iterator.next();
                if (t.getId().equals(muem.getParentId())){
                    if (null == t.getChild()){
                        List<Muem> muemList = new ArrayList<>();
                        t.setChild(muemList);
                    }
                    Muem child = new Muem();
                    BeanUtils.copyProperties(muem,child);
                    t.getChild().add(child);
                    iterator.remove();
                }
            }
            if (null != t.getChild()){
                this.recursion(t.getChild(),muems);
            }else{
                t.setChild(new ArrayList<>()); ;
            }
        }
    }
}

3、main方法测试

public static void main(String[] args) {
Muem muem1 = new Muem(1,null,"系统管理");
        Muem muem2 = new Muem(2,1,"权限");
        Muem muem3 = new Muem(3,1,"密码");
        Muem muem4 = new Muem(4,1,"用户");
        Muem muem5 = new Muem(5,1,"字典");
        Muem muem6 = new Muem(6,null,"数据统计");
        Muem muem7 = new Muem(7,6,"个人数据");
        Muem muem8 = new Muem(8,6,"团队");
        Muem muem9 = new Muem(9,0,"基础信息");
        Muem muem10 = new Muem(10,0,"其他信息");

        List<Muem> muems = new ArrayList<>();
        muems.add(muem1);
        muems.add(muem2);
        muems.add(muem3);
        muems.add(muem4);
        muems.add(muem5);
        muems.add(muem6);
        muems.add(muem7);
        muems.add(muem8);
        muems.add(muem9);
        muems.add(muem10);

        MenuTree menuTree = new MenuTree(muems);
        List<Muem> menuList = new ArrayList<>();
        menuList = menuTree.getParents(muems);
        String jsonOutput= JSON.toJSONString(menuList);
        System.out.println(jsonOutput);
}