ImageIO Error

Hello alls,

I try to implement Captchas IView

https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/com.sap.km.cm.docs/library/ep/6.0/how captchas can be helpful in securing enterprise portals.pdf

But I get error

java.lang.NoClassDefFoundError: javax/imageio/ImageIO

Can someone say to me, what is the matter?

Thanks