Sorting strings in a list based on indexes

Question

If i have an ArrayList of strings ["bb", "ab", "cf", "aa"] how can I sort alphabetically by the 1st or nth index and onward (if 1st index is the same character for other strings) ? Is there a method I can use to do so?

The list above, I would expect for index = 1

["aa", "bb", "ab", "cf"]

Another example would

["bab", "baa", "abbe", "cff"] would return

["baa", "bab", "abbe", "cff"]

Possible duplicate of [How to use Comparator in Java to sort](https://stackoverflow.com/questions/2839137/how-to-use-comparator-in-java-to-sort) (p.s. not the downvoter) — Alex Shesterov, Apr 06 '19 at 08:19
By using a comparator that extracts the nth character of both strings and compares them. Try something at least. — JB Nizet, Apr 06 '19 at 08:19

Stranger in the Q · Answer 1 · 2019-04-06T10:51:11.573

You can use Comparator.comparingInt to perform this sort:

Using index 0 to sort arrays:

String[] s = {"bb", "ab", "cf", "aa"};
Arrays.sort(s, Comparator.comparingInt(s1 -> s1.charAt(0)));
Arrays.asList(s).forEach(System.out::println);

or sort lists:

List<String> s = Arrays.asList("bb", "ab", "cf", "aa");
s.sort(Comparator.comparingInt(s2 -> s2.charAt(0)));
s.forEach(System.out::println);

Outputs:

ab
aa
bb
cf

Otherwise using index 1 for sort arrays:

String[] s = {"bb", "ab", "cf", "aa"};
Arrays.sort(s, Comparator.comparingInt(s2 -> s2.charAt(1)));
Arrays.asList(s).forEach(System.out::println);

or index 1 for sorting lists

List<String> s = Arrays.asList("bb", "ab", "cf", "aa");  
s.sort(Comparator.comparingInt(s2 -> s2.charAt(1)));
s.forEach(System.out::println);

Outputs:

aa
bb
ab
cf

PS: You question about java, but your strings and array like javascript..

MS90 · Answer 2 · 2019-04-06T08:34:41.570

Take a look at this simple example:

 public static void main(String[] args) {
        List<String> listOfStrings = new LinkedList<>();
        listOfStrings.add("aa");
        listOfStrings.add("bb");
        listOfStrings.add("ge");
        listOfStrings.add("be");
        System.out.println(Arrays.asList(listOfStrings));
        String getMe = listOfStrings.remove(3);
        listOfStrings.add(0, getMe);
        System.out.println(Arrays.asList(listOfStrings));
    }

LinkedList are good for insterting and removing elements and this can be done in O(1) (change it locally ), also I would like to mention that adding or removing a head of the list is done in O(1) too which is optimal for your cause.

Sorting strings in a list based on indexes

2 Answers2