Question

I have a TreeTable and would like to perform the sort by number and alphabetically when clicking on header.

Example:

• On a first click, I have to check that the column content is sorted by number
• If I click on another column that contains String data, I have to check that column content is sorted alphabetically.

Are there known functions that could I use?

I’ve used Collections for sorting number , but how do I can make the sort alphabetically ?
Collections.sor(myList) is OK for sorting by number but I would sort data alphabetically.

thanks

Answer 1

This can easily be done via Collections.sort(...). Create a copy of your list, sort it and check if they are equal.

Example:

List <String> copy = new ArrayList <String>(original);
Collections.sort(copy);
assertEquals(copy, original);

This can be done, if the elements in the list are comparable (i.e. are of type T implements Comparable <T>). Strings are comparable, and their default comparator sorts them alphabetically (though upper-case are always comes before lower-case)

You may also provide a Comparator for a more flexible sorting.

Here is a more complicated example.

List <String> unholyBible = new ArrayList <String>();
unholyBible.add("armageddon");
unholyBible.add("abyss");
unholyBible.add("Abaddon");
unholyBible.add("Antichrist");
Collections.sort(unholyBible);
System.out.println(unholyBible);

This will print us [Abaddon, Antichrist, abyss, armageddon]. This is because default comparation is case-sensitive. Lets fix it:

List <String> unholyBible = new ArrayList <String>();
unholyBible.add("armageddon");
unholyBible.add("abyss");
unholyBible.add("Abaddon");
unholyBible.add("Antichrist");
Collections.sort(unholyBible, new Comparator <String>() {
    public int compare(String o1, String o2){
        return o1.compareToIgnoreCase(o2);
    }
});
System.out.println(unholyBible);

This one prints [Abaddon, abyss, Antichrist, armageddon].

Now you may worship Satan in strict alphabetical order.

See also

• Comparator API
• Collections.sort(List, Comparator)