Source article: Passing a list as an argument to a vararg method
Use the toArray(T[] arr) method.
.getMap(locations.toArray(new WorldLocation[locations.size()]))
(toArray(new WorldLocation[0]) also works, but you would allocate a zero-length array for no reason.)
Here's a complete example:
public static void method(String... strs) {
for (String s : strs)
System.out.println(s);
}
...
List<String> strs = new ArrayList<String>();
strs.add("hello");
strs.add("world");
method(strs.toArray(new String[strs.size()]));
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...