Thread: TreeMap:

I decided to learn a little more about TreeMap and I am having some issues and was hoping for some advice.

package org.search.BFS;
 
import java.util.Random;
import java.util.TreeMap;
 
public class Graph 
{
	protected class node
	{
		int number;
		boolean visited;
	}
 
	protected TreeMap<node,Integer> tree = new TreeMap<node,Integer>();
 
	Graph()
	{
 
	}
	Graph(node s, int v) //constructor
	{
		tree.put(s,v);
	}
 
	void fillTree()
	{
	//fills the graph with 100 random numbers
	Random random = new Random();
	//create a new node in method
	node n = new node();
 
	for(int i=0;i<=100;i++)
	{
		n.number=random.nextInt(100); //add a random number to the node
		n.visited = false;//set to false inside node
		n=new node(); //create new node
		tree.put(n, i);//place node into tree
	}
 
	}
 
	void printTree()
	{
		int i =0;
		while(!tree.isEmpty())
		{
			System.out.println(tree.get(i));
			i++;
		}
	}
 
	public static void main(String [] args)
	{
		Graph graph = new Graph();
 
		graph.fillTree();
		graph.printTree();
	}
 
 
}

 
errors:
Exception in thread "main" java.lang.ClassCastException: org.search.BFS.Graph$node cannot be cast to java.lang.Comparable
	at java.util.TreeMap.compare(TreeMap.java:1188)
	at java.util.TreeMap.put(TreeMap.java:531)
	at org.search.BFS.Graph.fillTree(Graph.java:37)
	at org.search.BFS.Graph.main(Graph.java:56)

for(int i=0;i<=100;i++)
	{
		n.number=random.nextInt(100); //add a random number to the node
		n.visited = false;//set to false inside node
		tree.put(n, i);//place node into tree
		n=new node(); //create new node
	}

I seen that when I was reading through the errors. However I do not know how to compare them.

Yes... but the tone of your comment makes me think I should do it again. I read it with the preconceived notion that I had to do the comparing.