Arvore generica

// Baseada na Implementacao do Livro de Bruno Preiss 
public class GeneralTree {
    protected Object key;
    protected int degree;
    protected List list; 

    public Object getKey ()
	{ return key; }
	
	public GeneralTree (Object key) {
		this.key = key;
		degree = 0;
		list = new List ();
    }

    public GeneralTree getSubtree (int i) {
		if (i < 0 || i >= degree)
		    throw new IndexOutOfBoundsException ();
		Node ptr = list.getFirst ();
		for (int j = 0; j < i; ++j)
		    ptr = ptr.getNext ();
		return (GeneralTree) ptr.getData ();
    }

    public void attachSubtree (GeneralTree t) {
		list.insertAtBack (t);
		++degree;
    }

    public GeneralTree detachSubtree (GeneralTree t) {
		list.remove (t);
		--degree;
		return t;
    }
}

public class NaryTree {
    protected Object key;
    protected int degree;
    protected NaryTree[] subtree;

    public NaryTree (int degree) {
		key = null;
		this.degree = degree;
		subtree = null;
    }

    public NaryTree (int degree, Object key) {
		this.key = key;
		this.degree = degree;
		subtree = new NaryTree[degree];
		for (int i = 0; i < degree; ++i)
		    subtree [i] = new NaryTree (degree);
    }
    
    public boolean isEmpty () { return key == null; }

    public Object getKey (){
		if (isEmpty ())
		    throw new RuntimeException ();
		return key;
    }

    public void attachKey (Object object) {
		if (!isEmpty ())
		    throw new RuntimeException ();
		key = object;
		subtree = new NaryTree[degree];
		for (int i = 0; i < degree; ++i)
		    subtree [i] = new NaryTree (degree);
    }

    public NaryTree getSubtree (int i) {
		if (isEmpty ())
		    throw new RuntimeException ();
		return subtree [i];
    }

    public void attachSubtree (int i, NaryTree t) {
		if (isEmpty () || !subtree [i].isEmpty ())
		    throw new RuntimeException ();
		subtree [i] = t;
    }

    public NaryTree detachSubtree (int i) {
		if (isEmpty ())
		    throw new RuntimeException ();
		NaryTree result = subtree [i];
		subtree [i] = new NaryTree (degree);
		return result;
	    }
}