I want to sort an ArrayList of type String using a comparator. I have only found examples on how to do it if an ArrayList stores objects.
I have an ArrayList of strings that have 10 symbols and last 5 of those symbols are digits that form a number. I want to solve an array list in ascending order of those numbers that are at the end of each string. How can I do that?
Thanks!
This is one way to accomplish your task; sorted accepts a Comparator object.
List<String> result = myArrayList.stream().sorted(Comparator.comparingInt(e -> Integer.parseInt(e.substring(5))))
.collect(Collectors.toList());
or simply:
myArrayList.sort(Comparator.comparingInt(e -> Integer.parseInt(e.substring(5))));
Collections.sort can sort you a list with a Comparator. Plus you need String.substring:
Collections.sort(list, new Comparator<String>(){
@Override
public int compare(String o1, String o2) {
return o1.substring(5).compareTo(o2.substring(5));
}
});
Collections.sort(list, String::compareTo);
The above code does the job.
If you want more control, you could use/chain with one of the static methods available in the Comparator Interface.
Collectios.sort(list, Comparator.comparing(String::CompareTo).thenComparingInt(String::length));
Stringis anObject. What have you tried (exactly)? Let's see some code.private static ArrayList<String> allCodes = new ArrayList<String>(); //add some codes in .... private void sortAllCodesNumbers (){ Collections.sort(allCodes, allCodes.getCompByNum()); }public static Comparator<String> getCompByNum() { Comparator comp = new Comparator<String>(){ @Override public int compare(allBooks b1, allBooks b2) { String IDnumbers1 = b1.substring(AUTHOR_ID_LENGHT+GENRE_LENGTH); int number1 = Integer.parseInt(IDnumbers1); String IDnumbers2 = b2.substring(AUTHOR_ID_LENGHT+GENRE_LENGTH); int number2 = Integer.parseInt(IDnumbers1); return number1.compareTo(number2); } }; return comp; }