ZK - ZK Developer's Guide/ZK in Depth/Zscript, java, EL/Define class and methods in zscript

From Documentation

Thanks to the power of BeanShell, the implementation of Java classes can be done in zscript as follows.

<zscript>
    public class MyWindow extends Window {    
    }    
</zscript>
<window use="MyWindow"/>

And you can define methods in zscript

<window>
	<zscript><![CDATA[  
		public void sayHello(){
			alert("hello");
		}
	]]>
	</zscript>
	<button label="Say Hello!" onClick="sayHello()" />
</window>