...
| Code Block |
|---|
|
public static int cardinality(Object obj, final Collection col) {
int count = 0;
Iterator it = col.iterator();
while(it.hasNext()) {
Object elt = it.next();
if((null == obj && null == elt) || obj.equals(elt)) { // null pointer dereference
count++;
}
}
return count;
}
|
Compliant Solution
The straightforward solution to this issue is to decouple the null checks from the expression that invokes a method on the variable objThis compliant solution eliminates the null pointer dereference.
| Code Block |
|---|
|
ifpublic static int cardinality(Object obj, == nullfinal Collection col) {
for(int count = 0;
Iterator it = col.iterator();
while(it.hasNext();) {
// col isObject currentlyelt named coll= it.next();
if (it.next()null == null) {
count++;
}
}
} else {
for (Iterator it = col.iterator();it.hasNext();) { // col is currently named coll
if (obj.equals(it.next(obj && null == elt) ||
(null != obj && obj.equals(elt))) {
count++;
}
}
return count;
}
|
| Wiki Markup |
|---|
Null pointer dereferences can happen in many path dependent ways. Because of the limitations of automatic detection tools, code review and manual inspection of code are indispensable activities \[[Hovemeyer 07|AA. Java References#Hovemeyer 07]\]. Annotations for method parameters that must be non-null can also alleviate the problem to a certain extent by aiding automatic detection. |
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