VariableNode.java

public class VariableNode extends Node
{
    public String varName;
    public Parser parser;
    
    public VariableNode() {}
       
    public VariableNode(String varName, Parser parser)
    {
        this.varName = varName;
        this.parser = parser;
    }
    
    public Object eval()
    {        
        Object varValue = parser.getVariable(varName);
        if (varValue == null)
        {
            System.out.println("Undefined Variable...Var Name: " + varName);
            System.exit(1);
        }        
        return varValue;
    }
}