TreeSet<T> 简单实现

package com.mypack.ds;

import java.util.Random;

public class TreeSet<T>
{
    
    /**
     * @param args
     */
    public static void main(String[] args)
    {
        // TODO Auto-generated method stub
        TreeSet<Integer> tree = new TreeSet<Integer>();
        for (int i = 0; i < 20; i ++)
        {
            tree.add(new Random().nextInt(100));
        }
        System.out.println(tree);
    }
    
    private Entry<T> root;
    
    private volatile Entry<T> entry;
    
    public TreeSet()
    {
        
    }
    
    public void add(T node)
    {
        if (root == null)
        {
            entry = root;
            final Entry<T> tmp = entry;
            synchronized (TreeSet.class)
            {
                if (tmp == null)
                {
                    root = new Entry<T>(node);
                }
            }
        }
        else
        {
            insertNode(root, node);
        }
    }
    
    public String toString()
    {
        StringBuilder sb = new StringBuilder();
        
        travel(root, sb);
        
        return sb.toString();
    }
    
    void travel(Entry<T> root, StringBuilder sb)
    {
        if (root.left == null)
        {
            sb.append(root.value).append(",");
        }
        else
        {
            travel(root.left, sb);
        }
        sb.append(root.value).append(",");
        if (root.right == null)
        {
            sb.append(root.value).append(",");
        }
        else
        {
            travel(root.right, sb);
        }
    }
    
    synchronized void insertNode(Entry<T> obj, T node)
    {
        Comparable<T> c = (Comparable<T>)node;
        
        // right
        if (c.compareTo(obj.value) > 0)
        {
            if (obj.right != null)
            {
                insertNode(obj.right, node);
            }
            else
            {
                Entry<T> en = new Entry<T>(node);
                obj.right = en;
            }
        }
        // left
        else
        {
            if (obj.left == null)
            {
                Entry<T> en = new Entry<T>(node);
                obj.left = en;
            }
            else
            {
                insertNode(obj.left, node);
            }
        }
    }
    
    static class Entry<T>
    {
        Entry left;
        T value;
        Entry right;
        
        Entry(T value)
        {
            this.value = value;
        }
    }
    
}