TNode.java
public class TNode {
	protected int w;
    TNode lChild = null;
    TNode rChild = null;
    String huffCode = null;
    public TNode(int w,TNode l,TNode r) {
    	 this.w = w;
        lChild = l;
        rChild = r;
    }
   public TNode(int w)
    {  this.w = w;
    }
    public boolean isLeaf()
    {
        return (rChild==null && lChild == null);
    }
    public int getWeight()
    { return w;
    }
    public TNode leftChild()
    {  return lChild;
    }
    public TNode rightChild()
    {  return rChild;
}    
 public void setHuffCode(String str)
    {   huffCode = str;
    }
    public String getHuffCode()
    {  return huffCode;
    }
    
}


Tree.java
import java.util.*;

class Tree 
{
    
    protected TNode root;
    
    protected List<Integer> leafWList = new ArrayList<Integer>(); 
    
    protected List<TNode> tmpList = new LinkedList<TNode>();
    
    protected TNode[] leafArr = null;
    

    public void getLeafWeight()
    {
        Scanner scan = new Scanner(System.in);
        
        System.out.println("請輸入各葉子節點的權值，0為結束：");
        
        
        while(scan.hasNextInt())
        {
            int i = scan.nextInt();
            
            if(i==0)
                break;
            leafWList.add(new Integer(i));
        }
        
        scan = null;
        
        return ;
    }


    public TNode min()
    {
        Iterator<TNode> itr = tmpList.iterator();
        TNode minNode = itr.next();
        int min = minNode.getWeight();
        
        //找到最小的節點
        TNode tmpNode;
        while(itr.hasNext())
        {
            tmpNode = itr.next();
            if(tmpNode.getWeight()<min)
            {
                min = tmpNode.getWeight();
                minNode = tmpNode;
            }
        }
        

        //最小的節點移出臨時隊列
        tmpList.remove(minNode);
        
        //處理垃圾
        itr = null;
        tmpNode = null;
        
        return minNode;
        
    }
    
/**
* 根據權值創建葉子節點并加入臨時隊列
*
*/       
    public void makeLeafNode()
    {
        leafArr = new TNode[leafWList.size()];
        
        for(int i=0;i<leafWList.size();i++)
        {
            TNode node = new TNode(leafWList.get(i).intValue());
            leafArr[i] = node;
            tmpList.add(node);
        }
    }
    
/**
* 根據權值構造最優的二叉樹
*
*/     
    public void makeBestTree()
    {
        //根據權值創建葉子節點并加入臨時隊列
        makeLeafNode();
        
        TNode minNode1 = null,minNode2 = null;
        TNode node = null;
        //構造最優樹
        while(tmpList.size()!=1)
        {
            minNode1 = min();
            minNode2 = min();
            
            node = new TNode(minNode1.getWeight()+minNode2.getWeight(),minNode1,minNode2);
            tmpList.add(node); 
        }
        
        root = node;
        
    }
/**
* 先序遍歷的遞歸調用
*
*/      
    protected void preT(TNode t)
    {
        if(t.isLeaf())
        {
            System.out.print(t.getWeight() + " ");
            return ;
        }
        else
        {
            System.out.print(t.getWeight() + " ");
            preT(t.lChild);
            preT(t.rChild);
        }
    }
    
    
    
/**
* 先序遍歷最優二叉樹
*
*/      
    public void preOrderTraverse()
    {
        preT(root);
    }
    
    
    public static void main(String [] args)
    {
        Tree t = new Tree();
        t.getLeafWeight();
        t.makeBestTree();
        t.preOrderTraverse();
    }
}

HuffmanCode.java
public class HuffmanCode extends Tree
{
    public HuffmanCode()
    {
        init();
    }
    
/**
* 初始化節點值并構造最優二叉樹
*
*/
        
    public void init()
    {
        super.getLeafWeight();
        super.makeBestTree();
    }
    
/**
* 生成赫夫曼編碼的遞歸函數
*
* @param t TNode 當前遍歷節點
* @param s String 目前遍歷至此的赫夫曼編碼
*/
    protected void hufT(TNode t,String s)
    {
        if(t.isLeaf())
        {
            t.setHuffCode(s);
        }
        else
        {
            hufT(t.lChild,s+"0");
            hufT(t.rChild,s+"1");
        }
    }
    
/**
* 生成赫夫曼編碼的外部調用函數
*
*/   
    public void makeHuffCode()
    {
        hufT(root,"");
        
    }

/**
* 查看所有的赫夫曼編碼值
*
*/      
    public void viewHuffCode()
    {String S= new String();
     int L=S.length();
     float p;
     int t,n;
     t=0;n=0;
     
        for(int i=0;i<leafArr.length;i++)
        { S=leafArr[i].getHuffCode();
         L=S.length();
         t=leafArr[i].w*L+t;
         n=leafArr[i].w+n;
         
          System.out.println(leafArr[i].w + ": " +S+"   編碼長度為:   "+  L);
      }
       p=(float)t/n;
       System.out.println("最短編碼長度為:"+t+"/"+n+"="+p);
    }
    
    public static void main(String [] args)
    {
        HuffmanCode hc = new HuffmanCode();
        hc.makeHuffCode();
        hc.viewHuffCode();
    }
}