Why does my java code throw a null pointer exception - how to fix?

A common reason for Null Pointer Exceptions in Java is a variable redeclaration instead of instantiation. Learn what that means, how to avoid it, and how to spot it, in this presentation. # FAQ - why does my code throw a null pointer exception - common reason #1 Redeclaration - Using `@BeforeClass` or `@Before` can setup data for use in tests - Any 'variables' we instantiate need to be 'fields' rather than variables - We want to instantiate them in the setup method rather than redeclare them # Automatically Refactor prior to using `@Before...` - I might still want to use an `@BeforeClass` or `@Before` - To make the code readable - I could do that - but I don't think I would have declared a new variable after the refactorings because I have a working code example that I'm moving. # In General - Try to write one test at a time so that if you have a problem it is easier to identify where the problem is - Try to write working isolated tests and then refactor to a more general solution when you need it - that way, you know it was working, so you just have to work backwards to find out what went wrong - Try to use automated IDE refactoring rather than move code around manually - Use the IDE syntax highlighting to help spot any issues For more details see Blog Post: - http://blog.javafortesters.com/2017/08/faq-null-pointer-exception.html - http://testerhq.com/post/blogs/javafortesters/2017-08-29-faq-null-pointer-exception/ SlideShare: https://www.slideshare.net/eviltester/faq-why-does-my-code-throw-a-null-pointer-exception-common-reason-1-redeclaration