null
outside a declaration.
The main purpose of null
in Java is to denote uninitialized
reference variables. In rare cases, assigning a variable explicitly to null
is useful to aid garbage collection. However, using null
to denote a missing, not specified, or invalid value or a not
found element is considered bad practice and may make your code more prone to NullPointerExceptions
.
Instead, consider defining a sentinel object with the intended semantics
or use library types like Optional
to denote the absence of a value.
Example:
Integer convert(String s) {
Integer value;
try {
value = Integer.parseInt(s);
} catch (NumberFormatException e) {
// Warning: null is used to denote an 'invalid value'
value = null;
}
return value;
}
Use the Ignore assignments to fields option to ignore assignments to fields.