How to make an editor in java or groovy?

I'm not clear about the requirements. It'd be better if you could describe what you need to do a bit in more detail. Do you wish to develop a simple text editor with basic text editing functionalities or a code editor with support for multiple languages? Or do you wish to develop an image editor that will support the most common file formats like jpeg, png, gif? There could be an XML editor too that can be developed. While for the text editors the approach would be more or less the same, an image editor might require a different approach.

Always describe questions with all the possible, descriptive details so that it's easier for others to understand and reply to your questions.

editor like notepad