@Nullable annotation usage

Question

I saw some method in java declared as:

void foo(@Nullable Object obj)

{ ... }

What's the meaning of @Nullable here? Does it mean the input could be null? Without the annotation, the input can still be null, so I guess that's not just it?

Thanks

Answer 1

This delivers it explicit that the method allows null values, and that if you reverse the method, you should also acquire null values.

It also assists as a reference for code analyzers like FindBugs. For instance, if such a program dereferences its argument without holding for null first, FindBugs will release a warning.