When boxed type java.lang.Boolean is used as an expression to determine the control flow (as described in Java Language Specification §4.2.5 The boolean Type and
boolean Values) it will throw a NullPointerException if the value is null (as defined in Java Language Specification §5.1.8 Unboxing Conversion).
It is safer to avoid such conversion altogether and handle the null value explicitly.
Note, however, that no issues will be raised for Booleans that have already been null-checked or are marked @NonNull/@NotNull.
Noncompliant code example
Boolean b = getBoolean();
if (b) { // Noncompliant, it will throw NPE when b == null
foo();
} else {
bar();
}
Compliant solution
Boolean b = getBoolean();
if (Boolean.TRUE.equals(b)) {
foo();
} else {
bar(); // will be invoked for both b == false and b == null
}
Boolean b = getBoolean();
if(b != null){
String test = b ? "test" : "";
}
Exceptions
The issue is not raised if the expression is annotated @NonNull / @NotNull. This is useful if a boxed type is an
instantiation of a generic type parameter and cannot be avoided.
List<Boolean> list = new ArrayList<>();
list.add(true);
list.add(false);
list.forEach((@NonNull Boolean value) -> {
// Compliant
if(value) {
System.out.println("yes");
}
});
@NonNull Boolean someMethod() { /* ... */ }
// Compliant
if(someMethod()) { /* ... */ }
@NonNull Boolean boxedNonNull = Boolean.TRUE;
// Compliant
if(boxedNonNull) { /* ... */ }
