IfNode.java

public class IfNode extends Node
{
    public Node condition;
    public Node thenPart;
    public Node elsePart;
       
    public IfNode() {}
    
    public IfNode(Node condition, Node thenPart, Node elsePart)
    {
        this.condition = condition;
        this.thenPart = thenPart;
        this.elsePart = elsePart;
    }
       
    public Object eval()
    {
        Object ret = null;

        if ( (condition != null) && (thenPart != null))
            if ( ((Boolean) condition.eval()).booleanValue() )
                ret = thenPart.eval(); 
        
        if ( (condition != null) && (elsePart != null))            
            if ( !((Boolean) condition.eval()).booleanValue() )
                ret = elsePart.eval();
                
        return ret;
    }    
}