组合模式

• Composite
• 树状结构

  • abstract class Node{}
    class LeafNode extends Node{}
    class BranchNode extends Node{
        List<Node> nodes = new ArrayList<>();
    }
     
    tree(Node b, int depth) {
        b.print();
        if (b instanceof BranchNode) {
            for (Node n : ((BranchNode)b).nodes){
                tree(n, depth+1)
            }
        }
    }