NotOpNode.java

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

    public NotOpNode(Node node)
    {     
        this.node = node;
    }
    
    public boolean ToBoolean(Node node)
    {                
        Object res = node.eval();
        return ((Boolean) res).booleanValue();
    }    
    
    public Object eval()
    {                
        Object result = new Boolean(!ToBoolean(node));
        return result;
    }   
}