I am a beginner in Java and I have a run time error question. I have answered it correctly, however I do not completely understand the concept behind the answer. Could someone please explain why B is the right answer to the question, thank you:
Consider the following declarations:
private ArrayList<String> list;
...
public void printAll()
{
int index = 0;
while (index < list.size) {
index = index + 1;
System.out.println(list.get(index));
}
}
Assuming that list is not null, which one of the following is true about invocations of printAll()?
a)A run-time error occurs only if the list is empty.
b)A run-time error occurs only if the list is not empty.
c)A run-time error never occurs.
d)A run-time error always occurs.
e)A run-time error occurs whenever the list has an even length
while (index < list.size) {
index = index + 1;
System.out.println(list.get(index));
}
Here index
is incremented before accessing the list. So it reads one element ahead everytime. So run-time error when the list is not empty.
If the list is empty then the condition while (index < list.size)
will fail and hence the loop code that causes the run-time error will never be executed.
Although not relevant to your question, the correct code would be to increment the index
after reading:
while (index < list.size) {
System.out.println(list.get(index));
index = index + 1;
}