java achieve output tree

Whether in the form of this tree output in both linux and window, individuals feel very useful, occasionally think of it, try to do some tree output, the following is a specific code

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class mappingtool {

    public static void main(String[] args) {
        layer m = new layer("project");
        m.addNext(new layer("num 1"));
        m.addNext(new layer("num 2"));
        m.addNext(new layer("num 3"));
        layer layer1 = m.getLayerByNum(1);
        layer1.addNext(new layer("1.1"));
        layer1.addNext(new layer("1.2"));
        layer1.addNext(new layer("1.3"));

        layer layer1_1 = layer1.getLayerByNum(1);
        layer1_1.addNext(new layer("1.1.1"));
        layer1_1.addNext(new layer("1.1.2"));
        layer1_1.addNext(new layer("1.1.3"));

        layer layer2 = m.getLayerByNum(2);
        layer2.addNext(new layer("1.1"));
        layer2.addNext(new layer("1.2"));
        layer2.addNext(new layer("1.3"));
        layer layer3 = m.getLayerByNum(3);
        layer3.addNext(new layer("1.1"));
        layer3.addNext(new layer("1.2"));
        layer3.addNext(new layer("1.3"));





        System.out.println("" + m.toString());
    }


    static class layer {
        private String content = "default content";
        private String content_length = "                                                                          ";
        private int blank_num = 0;
        private List<layer> next = new ArrayList<>();

        public layer(String content) {
            this.content = content;
            this.blank_num = this.content.length();
            setBlank();
        }

        private void setBlank() {
            if (this.blank_num < this.content_length.length()) {
                this.content_length = this.content_length.substring(0,this.blank_num);
            } else {
                char[] chars = new char[this.blank_num];  Arrays.fill(chars,' ');
                this.content_length = new String(chars);
            }

        }

        public String getContent() {
            return content;
        }

        public void setContent(String content) {
            this.content = content;
        }

        public void addNext(layer layer){
            layer.blank_num = layer.content.length() + this.content_length.length();
            layer.setBlank();
            next.add(layer);
        }

        public layer getLayerByNum(int num){
            return this.next.get(num-1);
        }

        public void removeLayer(layer layer){
            next.remove(layer);
        }

        @Override
        public String toString() {
            String str = ""+this.content+"\n";
            if (this.next==null || this.next.size() < 1){
                return str;
            }
            for(int i=0;i<this.next.size();i++){
                str = str + this.content_length + "|___"+this.next.get(i).toString();
            }
            return str;
        }
    }
}

FIG output effect: