ClassCastException when casting object Array to Long array
I get this exception when i try to cast an Object array to a Long array.
Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.Long;
My keys in my hotelRooms map are Long, why it is not possible to cast. Does someone know how to solve this.
public class ObjectArrayToLongArrayTest {
private Map<Long, String[]> hotelRooms;
public static void main(String[] args) {
ObjectArrayToLongArrayTest objectArrayToLongArrayTest =
new ObjectArrayToLongArrayTest();
objectArrayToLongArrayTest.start();
objectArrayToLongArrayTest.findByCriteria(null);
}
private void start() {
hotelRooms = new HashMap<Long, String[]>();
// TODO insert here some test data.
hotelRooms.put(new Long(1), new String[] {
"best resort", "rotterdam", "2", "y", "129", "12-12-2008",
"11111111"
});
hotelRooms.put(new Long(2), new String[] {
"h开发者_如何学Cilton", "amsterdam", "4", "n", "350", "12-12-2009", "2222222"
});
hotelRooms.put(new Long(3), new String[] {
"golden tulip", "amsterdam", "2", "n", "120", "12-09-2009",
null
});
}
public long[] findByCriteria(String[] criteria) {
Long[] returnValues;
System.out.println("key of the hotelRoom Map" + hotelRooms.keySet());
if (criteria == null) {
returnValues = (Long[]) hotelRooms.keySet().toArray();
}
return null;
}
}
change
returnValues = (Long[]) hotelRooms.keySet().toArray();
to
returnValues = hotelRooms.keySet().toArray(new Long[hotelRooms.size()]);
and let me know if it works :-)
It's because Object[] Set.toArray()
returns an object array. You can't downcast the array to a more specific type. Use <T> T[]Set.toArray(T[] a)
instead. If the generic type method didn't exist you'd have to loop through each of the Objects in the return object array and cast each individually into a new Long array.
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