src/main/java/com/googlecode/objectify/ObjectifyFactory.java
public <T> Key<T> allocateId(final Class<T> clazz) {
		return allocateIds(clazz, 1).iterator().next();
	}
public <T> Key<T> allocateId(final Class<T> clazz) {
		return allocateIds(clazz, 1).iterator().next();
	}
Allocates a single id from the allocator for the specified kind.  Safe to use in concert
with the automatic generator.  This is just a convenience method for allocateIds().

@param clazz must be a registered entity class with a Long or long id field.
@return a key with an id that is unique to the kind