java - How to sort Alphanumeric String -

i have problem sorting strings include integers. if use below code sorting like: 1some, 2some, 20some, 21some, 3some, some

however want sorted like: 1some, 2some, 3some, 20some, 21some, some

how can this?

thanks!

collections.sort(selectednodes,     new comparator<defaultmutabletreenode>() {     @override     public int compare(defaultmutabletreenode o1,         defaultmutabletreenode o2) {         return o1.getuserobject().tostring()             .compareto(o2.getuserobject().tostring());     }     }); 

here self-contained example on how (not particularly optimized):

final pattern p = pattern.compile("^\\d+"); string[] examples = {     "1some", "2some", "20some", "21some", "3some", "some", "1abc", "abc" }; comparator<string> c = new comparator<string>() {     @override     public int compare(string object1, string object2) {         matcher m = p.matcher(object1);         integer number1 = null;         if (!m.find()) {             return object1.compareto(object2);         }         else {             integer number2 = null;             number1 = integer.parseint(m.group());             m = p.matcher(object2);             if (!m.find()) {                 return object1.compareto(object2);             }             else {                 number2 = integer.parseint(m.group());                 int comparison = number1.compareto(number2);                 if (comparison != 0) {                     return comparison;                 }                 else {                     return object1.compareto(object2);                 }             }         }     } }; list<string> exampleslist = new arraylist<string>(arrays.aslist(examples)); collections.sort(exampleslist, c); system.out.println(exampleslist); 

output

[1abc, 1some, 2some, 3some, 20some, 21some, abc, some] 

explanation

• the example uses constant pattern infer whether number in string's starting position.
• if not present in first string, compares second.
• if present indeed in first, checks second.
• if not present in second, compares 2 strings is, again
• if present in both, compares integers instead of whole strings, hence resulting in numerical comparison rather lexicographical one
• if number compare identical, goes lexicographic comparison of whole strings (thanks mihaic spotting one)