public class Main {

    public static void main(String[] args) {
        Comparator<String> comparator = new Comparator<String>() {
                @Override
                public int compare(String string_1, String string_2) {
                    ...
                }
        };
        
        TreeMap<String, String> treeMap = new TreeMap<String, String>(comparator);
        treeMap.put("COM1", "\\Device\\Serial0");
        treeMap.put("COM2", "\\Device\\Serial1");
        treeMap.put("COM8", "\\Device\\Nmserial0");
        treeMap.put("COM9", "\\Device\\Nmserial1");
        treeMap.put("COM10", "\\Device\\Nmserial2");
        treeMap.put("COM11", "\\Device\\Nmserial3");
    }
}