从辅助类的不同线程上的父类更新UI

I have a parent class which builds my UI (basically just a text box at the moment). I have created a secondary class which creates a new thread and I need to be able to update the textbox on the parent class from the new thread. Everything I try throws errors. I'm assuming I need to create some kind of dispatcher but my background is C# and I'm not 100% familiar on how to do this in Java.I have a parent class which builds my UI (basic