title: Require @NotNull and @Nullable annotations on all fields and parameters?
body: <p>Kotlin is a JVM language that has built in <a href="https://kotlinlang.org/docs/reference/null-safety.html" rel="noreferrer">support for nullable and non-null types</a>. Java, as we know, does not have this support.</p>
  
  <p>However, Java does have @Nullable and @NotNull (or similar) annotations provided through <a href="https://www.jetbrains.com/idea/help/nullable-and-notnull-annotations.html" rel="noreferrer">Jetbrains</a>, <a href="http://findbugs.sourceforge.net/api/edu/umd/cs/findbugs/annotations/package-summary.html" rel="noreferrer">FindBugs</a>, <a href="http://tools.android.com/tech-docs/support-annotations" rel="noreferrer">Android</a>, and <a href="https://jcp.org/en/jsr/detail?id=305" rel="noreferrer">JSR305</a>.</p>
  
  <p>Like Kotlin, I would like to require (via IDE) all Java parameters and fields to be annotated with one of these annotations. If possible, I would like to use CheckStyle, as I already have it integrated into our build workflow. However, I could not find any rules programmed for the purpose of requiring annotations in CheckStyle's <a href="http://checkstyle.sourceforge.net/checks.html" rel="noreferrer">list of checks</a>.</p>
  
  <p>How would I go about doing something like this?</p>