Thank you for your intention to contribute to the Apache OpenNLP project. As an open-source community, we highly appreciate external contributions to our project.
To make the process smooth for the project committers (those who review and accept changes) and contributors (those who propose new changes via pull requests), there are a few rules to follow.
Please check out the How to get involved to understand how contributions are made. A detailed list of coding standards can be found at Apache OpenNLP Code Conventions which also contains a list of coding guidelines that you should follow. For pull requests, there is a check list with criteria for acceptable contributions.