不使用递归,生成树结构

待我称王封你为后i 2024-03-25 21:42 17阅读 0赞

public static void main(String[] args) {
    
        List<Dept> depts = initListDept();
        
        List<Dept> nodes = treeList(depts);
    
        System.out.println(nodes);
    
    }
    
    public static List<Dept> treeList(List<Dept> depts) {
        // 整体思路: 循环非顶层,查找父级,并将自己设置到父级中
        // 用于根据ID查询部门使用
        Map<String, Dept> deptMap = new HashMap<>(depts.size());
        for (Dept dept : depts) {
            deptMap.put(dept.id, dept);
        }
    
        for (Dept child : depts) {
            // 找到父级
            String parentId = child.getParentId();
            Dept parent = deptMap.get(parentId);
            if (parent != null) {
                // 将自己添加到父级的子列表中
                parent.getChildren().add(child);
            }
    
        }
    
        // 舍弃方案: 循环嵌套易出现栈溢出
        /*for (Dept parent : depts) {
    
            //查询集合中父ID等于parent的ID的数据,存入children集合中
            for (Dept sub : depts) {
                if (sub.getParentId().equals(parent.getId())) {
                    parent.getChildren().add(sub);
                }
            }
        }
    */
        // 只保留顶层数据
        return depts.stream().filter(e -> "0".equals(e.getParentId())).collect(Collectors.toList());
    }
    
    public static List<Dept> initListDept() {
    
        ArrayList<Dept> depts = new ArrayList<>();
        depts.add(new Dept("1", "0", "父1"));
        depts.add(new Dept("2", "1", "子1"));
        depts.add(new Dept("3", "1", "子2"));
        depts.add(new Dept("4", "2", "子1-1"));
        depts.add(new Dept("5", "3", "子2-1"));
        depts.add(new Dept("6", "1", "子3"));
        depts.add(new Dept("7", "2", "子1-2"));
        depts.add(new Dept("8", "3", "子2-2"));
        depts.add(new Dept("9", "5", "子2-1-1"));
        return depts;
    }
    
    @Data
    public static class Dept {
        private String id;
        private String parentId;
        private String name;
        private List<Dept> children = new ArrayList<>();
    
        public Dept(String id, String parentId, String name) {
            this.id = id;
            this.parentId = parentId;
            this.name = name;
        }
    
    }