Java compare strings that have characters and numbers

Question

In Java , I want to compare and sort strings that contain a character and a number. For example:

A15, D35, A17, C45, B27, C30 should be sorted

A15 A17 B27 C30 C45 D35. I am not really sure how to compare two of those elements because they contain a string and a number. Can anyone help me please?

Answer 1

If your numbers are always two digits, then simply compare the whole things as strings. Numbers in decimal are strings too.

It's a different story if you need to sort A9, A54, and A123456 and want the numbers to sort by their numeric value. In that case you may need to write your own compare function that splits the string apart into its component parts.

Answer 2

An example of said compare function:

import java.util.Collections;
import java.util.Comparator;
import java.util.List;

import com.google.common.collect.Lists;

class Scratch {

    public static void main(String[] args) {
        final List<String> in = Lists.newArrayList("D35", "A1", "C7", "A25", "A131");

        Collections.sort(in, new Comparator<String>() {
            @Override
            public int compare(String left, String right) {
                int letter = Character.compare(left.charAt(0), right.charAt(0));
                if (0 != letter)
                    return letter;

                return Long.compare(Long.parseLong(left.substring(1)), Long.parseLong(right.substring(1)));
            }
        });

        System.out.println(in);
    }
}