help with java requirements

I need a simple app demonstrating the fallowing: - UI has a single field to allow users to enter text - UI has two buttons. One button adds a string to the collection and the other is to view a string from the collection. - UI has text fields for viewing the average length of strings in the collection and viewing the median length of strings in the collection. - Average and median text fields should be labeled Average and median text fields shows a maximum of two decimal places. - UI has a number picker control that lets the user select a valid index from the underlying collection. Number picker control should limit input to only valid indices.