When using null-related annotations at global scope level, for instance using javax.annotation.ParametersAreNonnullByDefault (from JSR-305) at package level, it means that all the parameters to all the methods included in the package will, or should, be considered Non-null. It is equivalent to annotating every parameter in every method with non-null annotations (such as @Nonnull).

The rule raises an issue every time a parameter could be null for a method invocation, where the method is annotated as forbidding null parameters.

Noncompliant Code Example

@javax.annotation.ParametersAreNonnullByDefault
class A {

  void foo() {
    bar(getValue()); // Noncompliant - method 'bar' do not expect 'null' values as parameter
  }

  void bar(Object o) { // 'o' is by contract expected never to be null
    // ...
  }

  @javax.annotation.CheckForNull
  abstract Object getValue();
}

Compliant Solution

Two solutions are possible:

@javax.annotation.ParametersAreNonnullByDefault
abstract class A {

  void foo() {
      Object o = getValue();
      if (o != null) {
        bar(); // Compliant - 'o' can not be null
      }
  }

  void bar(Object o) {
    // ...
  }

  @javax.annotation.CheckForNull
  abstract Object getValue();
}

or

@javax.annotation.ParametersAreNonnullByDefault
abstract class A {

  void foo() {
    bar(getValue());
  }

  void bar(@javax.annotation.Nullable Object o) { // annotation was missing
    // ...
  }

  @javax.annotation.CheckForNull
  abstract Object getValue();
}