Returns a zero-length array or empty collection, do not return null

1. Returns a zero-length array

private final List cheesesInStock = ...;public Cheese[] getCheeses(){if (cheesesInStock.size() == 0)return null;} 

It is counterintuitive to treat the situation where there is no cheese (Cheese) available as a special case.Doing so would require the client to have additional code to handle the null return value, for example:

Cheese[] cheeses = shop.getCheeses();if(cheeses != null && Arrays.asList(cheeses).contains(Cheese.STILTON)){System.out.println("Very good, just right");}

Instead of this code:

if( Arrays.asList(cheeses).contains(Cheese.STILTON)){System.out.println("Very good, just right");}

This is error-prone because Programmers writing client-side programs may forget to write such specialized code to handle null return values, such mistakes may go unnoticed for years.

Sometimes some people think that a null return value is better than a zero-length array because it avoids allocating an array