public class HuffmanNode implements Comparable, Cloneable {
    protected int key;              // 權值
    protected HuffmanNode left;     // 左孩子
    protected HuffmanNode right;    // 右孩子
    protected HuffmanNode parent;   // 父結點

    protected HuffmanNode(int key, HuffmanNode left, HuffmanNode right, HuffmanNode parent) {
        this.key = key;
        this.left = left;
        this.right = right;
        this.parent = parent;
    }

    @Override
    public Object clone() {
        Object obj=null;

        try {
            obj = (HuffmanNode)super.clone();//Object 中的clone()識別出你要複製的是哪一個物件。    
        } catch(CloneNotSupportedException e) {
            System.out.println(e.toString());
        }

        return obj;    
    }

    @Override
    public int compareTo(Object obj) {
        return this.key - ((HuffmanNode)obj).key;
    }
}