NegOpNode.java

public class NegOpNode extends Node
{
    public Node node;
    
    public NegOpNode() {}

    public NegOpNode(Node node)
    {     
        this.node = node;
    }

    public int ToInt(Node node)
    {
        Object res = node.eval();
        return ((Integer) res).intValue();
    }
        
    public Object eval()
    {                
        Object result = new Integer(-ToInt(node));
        return result;
    }       
}