comparator with null values

java comparator
pvgoddijn picture pvgoddijn · Mar 8, 2010 · Viewed 55.6k times · Source

We have some code which sorts a list of addresses based on the distance between their coordinates. this is done through collections.sort with a custom comparator.

However from time to time an address without coordinates is in the list causing a NullPointerException. My initial idea to fix this was to have the comparator return 0 as distance for addresses where at least one of the coordinates is null. I fear this might lead to corruption of the order the 'valid' elements in the list.

so is returning a '0' values for null data in a comparator ok, or is there a cleaner way to resolve this?

Answer

Sjoerd picture Sjoerd · Mar 8, 2010

Handle it like null means infinitely far away. Thus:

  • comp(1234, null) == -1
  • comp(null, null) == 0
  • comp(null, 1234) == 1

With this, you get a consistent ordering.

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