Null pointer dereferencing refers to treating a null variable as if it were a valid object or field and proceeding to use it without checking its state. Typically, this condition results in a NullPointerException which may lead to sometimes result in denial of service. While other runtime exceptions can produce similar effects, NullPointerException is often found to be the most frequent show-stopper.
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if (obj == null) {
for(Iterator it = col.iterator();it.hasNext();) { // col is currently named coll
if (it.next() == null) {
count++;
}
}
} else {
for (Iterator it = col.iterator();it.hasNext();) { // col is currently named coll
if (obj.equals(it.next())) {
count++;
}
}
}
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DereferencesNull ofpointer nulldereferences pointers can happen in many path dependent ways. Due to the limitations of automatic detection tools, code review and manual inspection of code are inevitableindispensable activities \[[Hovemeyer 07|AA. Java References#Hovemeyer 07]\]. Annotations for method parameters that must be non-null can also alleviate the occurrencesproblem to a certain extent by aiding automatic detection. |
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