Your first step would be to become more familiar with Java itself, as you will need this foundation before you do anything else. Visit The Java Tutorials first and learn some of the basics. Once you've mastered the basics of Java, and understand GUI development, you can move forward to reading data from an Excel file. I recommend Apache POI as a great tool to read data from Excel.
Your next step is of course to learn about graphs and plotting in Java, here you might find something like JFreeChart of great help.
Everything said here is feasible and practicable in Java; it only depends on your degree of dedication and desire to devote some time to creating this solution.
If you choose not to develop your own system, why not use LibreOffice or Microsoft Excel instead? Both programs can open documents, extract data, and produce charts, and they both offer strong features that will meet your needs.