calling Query from RTC server and extract the result

        // do something with the work item
        processed++;

And the aforementioned work item commandline has all the code you can asks for.
Otherwise read:

• https://rsjazz.wordpress.com/2015/09/30/learning-to-fly-getting-started-with-the-rtc-java-apis/

• https://rsjazz.wordpress.com/2013/03/20/understanding-and-using-the-rtc-java-client-api/

• https://rsjazz.wordpress.com/2013/01/02/working-with-work-item-attributes/

 i need to extract values from workItem by java API client not by  A RTC WorkItem Command Line Version 3.0 

I advise to read the articles mentioned and download the attached code or look at the code examples in some of the posts. There are tons of code examples in that blog that other people are able to read and use easily enough.

Read

• https://rsjazz.wordpress.com/2013/03/20/understanding-and-using-the-rtc-java-client-api/

• https://rsjazz.wordpress.com/2013/01/02/working-with-work-item-attributes/