How to sort a list of stings by number letter first and then number

Question

I have a string list as follows:

(2D, 1D, 1Y, 23M, 4M, 2Y, 12D)

How can I sort it alphabetically and then numerically?

I expect

(1D, 2D, 12D, 4M, 23M, 1Y, 2Y)

I tried this but it didn't work.

Collections.sort(myList, new MyComparator());

public class MyComparator implements Comparator {

    @Override
    public int compare(Object o1, Object o2) {

        String s1 = (String)o1;
        String s2 = (String)o2;
        String strPart1 = s1.split("")[1];
        int intPart1 = Integer.parseInt(s1.split("")[0]);

        String strPart2 = s2.split("")[1];
        int intPart2 = Integer.parseInt(s2.split("")[0]);

        int strCompareResult = strPart1.compareTo(strPart2);
        if(0 == strCompareResult )
        {
            return intPart1 - intPart2;
        }
        else
        {
            return strCompareResult;
        }
    }

}

However this did not work.

Answer 1

You can sort first by the last character, then parse the other characters as an int. The Comparator can be written more easily with the Comparator.comparing and .thenComparing methods.

myList.sort(Comparator.comparing((String s) -> s.charAt(s.length() - 1))
    .thenComparingInt(s -> Integer.parseInt(s.substring(0, s.length() - 1))));