Breadth-first search and depth-first search Java implementation

BFSDFS.java

Class Main {
	public void bfs()
	{
		// BFS uses Queue data structure
		Queue queue = new LinkedList();
		queue.add(this.rootNode);
		printNode(this.rootNode);
		rootNode.visited = true;
		while(!queue.isEmpty()) {
			Node node = (Node)queue.remove();
			Node child=null;
			while((child=getUnvisitedChildNode(node))!=null) {
				child.visited=true;
				printNode(child);
				queue.add(child);
			}
		}
		// Clear visited property of nodes
		clearNodes();
	}

	public void dfs() {
		// DFS uses Stack data structure
		Stack stack = new Stack();
		stack.push(this.rootNode);
		rootNode.visited=true;
		printNode(rootNode);
		while(!stack.isEmpty()) {
			Node node = (Node)s.peek();
			Node child = getUnvisitedChildNode(n);
			if(child != null) {
				child.visited = true;
				printNode(child);
				s.push(child);
			}
			else {
				s.pop();
			}
		}
		// Clear visited property of nodes
		clearNodes();
	}
}


Class Node {
   Char data;
   Public Node(char c) {
      this.data=c;
   }
}

cool!

In DFS method, why not just use pop() instead of peek()?

What I find odd is that the code marks nodes visited without checking if they've already been visited...
If they've already been visited, shouldn't they be ignored?

Nice implemetation.

you can avoid casting by using type parameters. Queue<Node> queue Stack<Node> stack

class Node {
        List<Node> children;
        boolean visited = false;
        Node getUnvisitedChildNode(){
            return children.stream()
                    .filter(n -> ! n.visited)
                    .findFirst().orElse(null);
        }
    }

@dkonayuki its ok peek, since in DFS she needs to revisit nodes and ask for other children.

Answer @dkonayuki,It would break the stack chain and without missing the right child node, if its use pop().

I realize this is a little pedantic, but these are Breadth and Depth first traversals not searches. They simply visit all nodes, not search for a specific node/value.