TreeMock.pde

void setup() {
  NodeFolder root = new NodeFolder("root");
  root.addChild(new IntNode("nerdsSniped", 32));
  root.addChild(new StringNode("cheese", "gouda"));
  
  NodeFolder cats = new NodeFolder("cats");
  cats.addChild(new IntNode("kittens", 3));
  cats.addChild(new IntNode("chomkers", 7));
  StringNode catSentiment = new StringNode("sentiment", "cute");
  cats.addChild(catSentiment);
  root.addChild(cats);

  NodeFolder dogs = new NodeFolder("dogs");
  dogs.addChild(new IntNode("puppers", 8));
  dogs.addChild(new IntNode("fluffers", 2));
  StringNode dogSentiment = new StringNode("sentiment", "yummy");
  dogs.addChild(dogSentiment);
  root.addChild(dogs);
  
  prettyPrintTree(root);
  
  copyValue(catSentiment, dogSentiment);
}

void copyValue(AbstractNode source, AbstractNode target){
  // TODO pls implement me in a nice generic way 
  // without the ugly a.getClass().getSimpleName().equals(b.getClass().getSimpleName()) to check for valid casts
}

abstract class AbstractNode {
  String name;
  boolean isFolder = false;

  AbstractNode(String name) {
    this.name = name;
  }

  String getPrintableValue() {
    return null;
  }
}

class NodeFolder extends AbstractNode {
  ArrayList<AbstractNode> children = new ArrayList<AbstractNode>(); 

  NodeFolder(String name) {
    super(name);
    isFolder = true;
  }

  void addChild(AbstractNode node) {
    children.add(node);
  }
}

class IntNode extends AbstractNode {
  int valueInt;

  IntNode(String name, int value) {
    super(name);
    this.valueInt = value;
  }

  String getPrintableValue() {
    return String.valueOf(valueInt);
  }
}

class StringNode extends AbstractNode {
  String valueString;

  StringNode(String name, String valueString) {
    super(name);
    this.valueString = valueString;
  }

  String getPrintableValue() {
    return String.valueOf(valueString);
  }
}


static void prettyPrintTree(NodeFolder root) {
  StringBuilder sb = new StringBuilder();
  buildPrettyPrintedTreeString(root, 1, sb);
  println(sb);
}

private static void buildPrettyPrintedTreeString(AbstractNode node, int depth, StringBuilder outputBuilder) {
  StringBuilder prefix = new StringBuilder();
  boolean hasChildren = node.isFolder && ((NodeFolder) node).children.size() > 0;

  for (int i = 0; i < depth; i++) {
    boolean atMaxDepth = i == depth - 1;
    if (atMaxDepth) {
      prefix.append(hasChildren ? "+ " : "- ");
    } else {
      prefix.append("|  ");
    }
  }

  String nodeValue = node.getPrintableValue();
  boolean hasValue = nodeValue != null && nodeValue.length() > 0;

  outputBuilder.append(prefix)
    .append(node.name)
    .append(hasValue ? ": " : "")
    .append(nodeValue == null ? "" : nodeValue)
    .append("\n");

  if (node.isFolder) {
    NodeFolder folder = (NodeFolder) node;
    for (AbstractNode child : folder.children) {
      buildPrettyPrintedTreeString(child, depth + 1, outputBuilder);
    }
  }
}