What-Nullable-to-Use-In-Java-As-Of-2023-JDK21

https://stackoverflow.com/questions/76630457/what-nullable-to-use-in-java-as-of-2023-jdk21

1. javax 已经被替换为了 jarkarta
2. 统一使用 https://checkerframework.org/manual/#nullness-checker 就好了