Suppose I am implementing a sorted collection (simple example - a Set based on a sorted array.) Consider this (incomplete) implementation:
import java.util.*;
public class SortedArraySet<E> extends AbstractSet<E> {
@SuppressWarnings("unchecked")
public SortedArraySet(Collection<E> source, Comparator<E> comparator) {
this.comparator = (Comparator<Object>) comparator;
this.array = source.toArray();
Collections.sort(Arrays.asList(array), this.comparator);
}
@Override
public boolean contains(Object key) {
return Collections.binarySearch(Arrays.asList(array), key, comparator) >= 0;
}
private final Object[] array;
private final Comparator<Object> comparator;
}
Now let's create a set of integers
Set<Integer> s = new SortedArraySet<Integer>(Arrays.asList(1, 2, 3), null);
And test whether it contains some specific values:
System.out.println(s.contains(2));
System.out.println(s.contains(42));
System.out.println(s.contains("42"));
The third line above will throw a ClassCastException. Not what I want. I would prefer it to return false (as HashSet does.)
I can get this behaviour by catching the exception and returning false:
@Override
public boolean contains(Object key) {
try {
return Collections.binarySearch(Arrays.asList(array), key, comparator) >= 0;
} catch (ClassCastException e) {
return false;
}
}
Assuming the source collection is correctly typed, what could go wrong if I do this?
