java - My treemap breaks after sorting it because "comparator used for the treemap is inconsistent with equals" -

i needed sort treemap based on it's value. requirements of i'm doing such have use sorted map. tried solution here: sort map<key, value> values (java) comments say, make getting values map not work. so, instead did following:

class sorter implements comparator<string> {     map<string, integer> _referencemap;     public boolean sortdone = false;     public sorter(map<string, integer> referencemap) {         _referencemap = referencemap;     }     public int compare(string a, string b) {         return sortdone ? a.compareto(b) : _referencemap.get(a) >= _referencemap.get(b) ? -1 : 1;     } } 

so leave sortdone false until i'm finished sorting map, , switch sortdone true compares things normal. problem is, still cannot items map. when mymap.get(/anything/) null still.

i not understand comparator inconsistent equals means.

i not understand comparator inconsistent equals means.

as per contract of comparable interface.

the natural ordering class c said consistent equals if , if e1.compareto(e2) == 0 has same boolean value e1.equals(e2) every e1 , e2 of class c. note null not instance of class, , e.compareto(null) should throw nullpointerexception though e.equals(null) returns false.

it recommended (though not required) natural orderings consistent equals.

i believe need change line :

 _referencemap.get(a) >= _referencemap.get(b) ? -1 : 1; 

to

 _referencemap.get(a).compareto(_referencemap.get(b)); 

since if integer returned _referencemap.get(a) == in value integer returned _referencemap.get(b) should ideally return 0, not -1.