null's in lists are not handled correctly for unique(), sort()

In DefaultGroovyMethods.java, locate the inner class NumberComparator.

Instead of
public int compare(Object o1, Object o2) {
if (o1 instanceof Number && o2 instanceof Number) {
...

check for null first:

public int compare(Object o1, Object o2) {
if (o1 == null)

else if (o2 == null)

else if (o1 instanceof Number && o2 instanceof Number) {
...

This solves the NPE problem.

Just discovered the code tag ...

In DefaultGroovyMethods.java, locate the inner class NumberComparator.

Instead of

public int compare(Object o1, Object o2) {
  if (o1 instanceof Number && o2 instanceof Number) {
    ...

check for null first:

public int compare(Object o1, Object o2) {
  if (o1 == null) { 
    return o2==null?0:-1; 
  } else if (o2 == null) {
    return 1; 
  } else if (o1 instanceof Number && o2 instanceof Number) {
    ...

This solves the NPE problem.

Patch and tests added.

I believe this is broken again. I had a list that held objects whose properties (which I'm sorting on) could be null and received a NPE. ie->
class test

My collection would contain 10 test objects, some with a sortValue, some without. When I sort by this value, I get an NPE at the first null value. Shouldn't the nulls float to the end?

null is the smallest value, so having it at the beginning is ok I think

There is a little bit more we could do to get rid of a NPE here. I'll investigate.

Workaround in the meantime is to use the spaceship operator version, i.e. instead of:

list.sort{ it?.sortValue }

use:

list.sort{ a, b -> a?.sortValue <=> b?.sortValue }