Re: a question for sorting keys in Map
www <www@nospam.com> writes:
I have a Map, actually a TreeMap, which will automatically sort the
keys alphabetically.
True.
The keys are Strings, like "VARIABLE" + i, e.g:
VARIABLE0, VARIABLE1, VARIABLE2, etc.
....
But, if the total number of entries > 10, the sorted order is not what
I want:
VARIABLE0
VARIABLE1
VARIABLE10
VARIABLE11
VARIABLE12
..
VARIABLE2
VARIABLE20
....
I want the order be:
VARIABLE0
VARIABLE1
VARIABLE2
..
VARIABLE9
VARIABLE10
VARIABLE11
...
As you said, the default order of comparison on strings is lexical, so
that is what you get.
You need to make a different comparison, and provide it to the TreeSet
as a Comparator.
Try, e.g.,
public static class VariableComparator implements Comparator<String> {
public int compare(String a, String b) {
int res = a.length() - b.length();
if (res == 0) {
res = a.substring(8).compareTo(b.substring(8));
}
return res;
}
}
It assumes that the strings do in fact start with "VARIABLE" and are
followed by the number.
Can you help me to achieve this? Thank you very much.
You might want to reconsider the approach. All you seem to need is a
set of numbers. You can always prefix with "VARIABLE" later.
A BitSet would perhaps suffice.
/L
--
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