What should methods return arrays or Collections?

To prolong Paul River's Weblog: By returning arrays we have a temporary advantage of typed objects(untill we java 5). There are many other advantages if a method returns Collections, We can decorate collections as needed.

• We can implement lazy loading returned objects very easily (with arrays also it may be possible by proxies etc in a long way).
• We can easily return (private) inner data (unmodifiable), instead of returning new cloned array each time.
• We can share data between multiple threads.
• Collection is as simple to use as an array type.

In summary returned collection can be changed to any sub type collection (which is very very useful from implementors perspective) with minimal client changes.