best practices java javascript
Every codebase depends on multiple external libraries. It is a good idea to stay up to date with external dependencies. It is important to update all security related stuff and it might be helpful or fun to use latest features. I’m going to share my way of staying up to date with external dependencies in maven, gradle and npm.
Private final field modification is possible and it doesn’t require a lot of work. Since you should not use this mechanism in real life there are cases when it is useful. For example this how is Hibernate using this to hydrate final entity fields.
But when using final fields with Hibernate you should be extra careful how you declare them.
A few days ago I’ve stumbled upon SQL query performance issue. Git claims that I was the author so maybe that’s the reason I remember this feature. There was like 3 classes, everything was super easy and super fast all I needed to do was to let Hibernate do its thing. Then time passed, new features were requested, the model becomes more complex, the number of rows increased to ~4 million and original query became too slow.
When working on query optimization I was really happy to find that detailed tests are in place. With proper test setup I was able to test my new query to make sure all requirements are met and then quickly copy paste query to sqldeveloper run it on a test environment and verify if performance is acceptable. It wasn’t simple query and it took me some time to figure out how to make it quick and work exactly as old one. That was the time I was really glad that we invested in detailed unit tests in the beginning.
Sometimes when unit tests setup is complex we are tempted to take shortcuts and write single setup for all tests which will save as few keystrokes. In the time of writing the test it might feel like a good idea to configure complex unit test setup and reuse it in all test. This way we avoid code duplication and we create a more condensed test. This approach looks good only in the time of the writing tests. Then there is a time when unit tests must be maintained. This is the time when you usually realize that saving few keystrokes wasn’t such a good idea.
HashCode and equals implementations are hard. Usually, it’s tricky to properly implement hashCode and equals method to fully fulfill contract from Java documentation. I’m going to focus on just one the point from the hashCode contract:
whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer.
Read it already? Do it again. Let it sink and think about impact of “hashCode method must consistently return the same integer”