Menu
FindBugs complains about Possible null pointer dereference of str1 on branch that might be infeasible in Comparator.compareStrings(String, String) in this method:
private static int compareStrings(final String str1, final String str2) {
if ((str1 == null) && (str2 == null)) {
return COMPARE_ABSENT;
}
if ((str1 == null) && (str2 != null)) {
return COMPARE_DIFFERS;
}
if ((str1 != null) && (str2 == null)) {
return COMPARE_DIFFERS;
}
return str1.equals(str2) ? COMPARE_EQUALS : COMPARE_DIFFERS;
}
In Eclipse, I also see a warning on the last line (str1 may be null).
Under what circumstances can str1 be null in return str1.equals(str2) ? COMPARE_EQUALS : COMPARE_DIFFERS; (given that the first two if blocks cover the situations, when str1 is null) ?
366
You can assign null to a variable to denote that currently that variable does not have any value but it will have later on. A null means absence of a value. In the above example, null is assigned to a variable myVar. It means we have defined a variable but have not assigned any value yet, so value is absence.
If a reference points to null , it simply means that there is no value associated with it. Technically speaking, the memory location assigned to the reference contains the value 0 (all bits at zero), or any other value that denotes null in the given environment.
To set the value of a variable is it's equal to null , use the nullish coalescing operator, e.g. myVar = myVar ?? 'new value' . The nullish coalescing operator returns the right-hand side operand if the left-hand side evaluates to null or undefined , otherwise it returns the left-hand side operand.
'Null' in JavaScript If you wish to shred a variable off its assigned value, you can simply assign 'null' to it. Besides this, like any other object, it is never implicitly assigned to a variable by JavaScript. Upon execution, the code will print null.
You can avoid the warning by rearranging the if statements :
private static int compareStrings(final String str1, final String str2) {
if (str1 == null) {
if (str2 == null)) {
return COMPARE_ABSENT;
} else {
return COMPARE_DIFFERS;
}
} else {
if (str2 == null)) {
return COMPARE_DIFFERS;
} else {
return str1.equals(str2) ? COMPARE_EQUALS : COMPARE_DIFFERS;
}
}
}
At the point where you call str1.equals(str2), str1 cannot be null. You should suppress this warning at that location.
34
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
