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javaannotations

@Nullable annotation usage

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?

Solution

  • It makes it clear that the method accepts null values, and that if you override the method, you should also accept null values.

    It also serves as a hint for code analyzers like FindBugs. For example, if such a method dereferences its argument without checking for null first, FindBugs will emit a warning.