I still feel confused when I want to customize the way of sorting for array and collections in java. And here is a good example of how to write a customized sorting function to sort string array:
Comparator<String> comp = new Comparator<String>(){
@Override
public int compare(String str1, String str2){
String s1 = str1 + str2;
String s2 = str2 + str1;
return s2.compareTo(s1); // reverse order here, so we can do append() later
}
};
Arrays.sort(s_num, comp);