Java converts a set of data into tree data

data 
{"parentID": 0,"sequence": 0,"id": 1,"leaf": true,"children": []} 
{"parentID": 0,"sequence": 0,"id": 2,"leaf": true,"children": []}

requirements: efficiency

Java
Apr.28,2022

two for loops. I can't think of any other good way for the time being. 

public class Test {
    public static void main(String[] args) throws Exception {
        String json = "[{\"parentID\": 0,\"sequence\": 0,\"id\": 1,\"leaf\": true,\"children\": []},         {\"parentID\": 0,\"sequence\": 0,\"id\": 2,\"leaf\": true,\"children\": []},         {\"parentID\": 1,\"sequence\": 0,\"id\": 3,\"leaf\": true,\"children\": []},         {\"parentID\": 2,\"sequence\": 0,\"id\": 4,\"leaf\": true,\"children\": []},         {\"parentID\": 2,\"sequence\": 0,\"id\": 5,\"leaf\": true,\"children\": []}]";
        List<Root> rootList1 = JsonUtil.toList(json, Root.class);        
        Set<Integer> idSet = new HashSet<Integer>();    
        for(Root r : rootList1){
            idSet.add(r.getId());
        }
        for(Root r : rootList1){
            if(!idSet.contains(r.getParentID())){
                System.out.println(r);
            }
        }
    }
}

class Root{
    private Integer parentID;
    
    private Integer sequence;
    
    private Integer id;
    
    private boolean leaf;
    
    private List<Root> children;

    public Integer getParentID() {
        return parentID;
    }

    public void setParentID(Integer parentID) {
        this.parentID = parentID;
    }

    public Integer getSequence() {
        return sequence;
    }

    public void setSequence(Integer sequence) {
        this.sequence = sequence;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public boolean isLeaf() {
        return leaf;
    }

    public void setLeaf(boolean leaf) {
        this.leaf = leaf;
    }

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

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

    @Override
    public String toString() {
        return "Root [parentID=" + parentID + ", sequence=" + sequence
                + ", id=" + id + ", leaf=" + leaf + ", children=" + children
                + "]";
    }
}

Previous: The page refresh will trigger updateAppMessageShareData.

Next: Vue traverses json data

css mysql arrays josn react html typescript webpack npm sass R objective-c .net sql-server jquery python-3.x angularjs django angular excel regex iphone ajax linux xml pandas vba spring database wordpress string wpf xcode windows bash postgresql oracle multithreading eclipse list firebase algorithm macos forms image scala visual-studio azure bootstrap spring-boot react-native python-2.7 docker performance function winforms matlab powershell apache dataframe api sqlite numpy rest shell selenium flutter dart maven loops qt swing android-studio csv express file class tensorflow sorting codeigniter perl
© 2021 CodesHelper
Advertising Contact us About us
Menu