How to print binary tree diagram?

Question

How can I print a binary tree in Java so that the output is like:

   4 
  / \ 
 2   5 

My node:

public class Node<A extends Comparable> {
    Node<A> left, right;
    A data;

    public Node(A data){
        this.data = data;
    }
}

Answer 1

Print a [large] tree by lines.

output example:

z
├── c
│   ├── a
│   └── b
├── d
├── e
│   └── asdf
└── f

code:

public class TreeNode {

    final String name;
    final List<TreeNode> children;

    public TreeNode(String name, List<TreeNode> children) {
        this.name = name;
        this.children = children;
    }

    public String toString() {
        StringBuilder buffer = new StringBuilder(50);
        print(buffer, "", "");
        return buffer.toString();
    }

    private void print(StringBuilder buffer, String prefix, String childrenPrefix) {
        buffer.append(prefix);
        buffer.append(name);
        buffer.append('\n');
        for (Iterator<TreeNode> it = children.iterator(); it.hasNext();) {
            TreeNode next = it.next();
            if (it.hasNext()) {
                next.print(buffer, childrenPrefix + "├── ", childrenPrefix + "│   ");
            } else {
                next.print(buffer, childrenPrefix + "└── ", childrenPrefix + "    ");
            }
        }
    }
}

P.S. This answer doesn't exactly focus on "binary" trees -- instead, it prints all kinds of trees. Solution is inspired by the "tree" command in linux.