How to sort alphabetically while ignoring case sensitive?

Question

Collections.sort(listToSort, String.CASE_INSENSITIVE_ORDER);

It is very unclear what you are trying to do, but you can sort a list like this:

List<String> fruits = new ArrayList<String>(7);

fruits.add("Pineapple");
fruits.add("apple");
fruits.add("apricot");
fruits.add("Banana");
fruits.add("mango");
fruits.add("melon");        
fruits.add("peach");

System.out.println("Unsorted: " + fruits);

Collections.sort(fruits, new Comparator<String>() {
    @Override
    public int compare(String o1, String o2) {              
        return o1.compareToIgnoreCase(o2);
    }
});

System.out.println("Sorted: " + fruits);

Collections.sort() lets you pass a custom comparator for ordering. For case insensitive ordering String class provides a static final comparator called CASE_INSENSITIVE_ORDER.

So in your case all that's needed is:

Collections.sort(caps, String.CASE_INSENSITIVE_ORDER);

Here's a plain java example of the best way to do it:

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

public class Sorter {
    String fruits[] = new String[7];
    List<String> lst;

    Sorter() {
        lst = new ArrayList<String>();
        // initialise UNSORTED array
        fruits[0] = "Melon"; fruits[1] = "apricot"; fruits[2] = "peach";
        fruits[3] = "mango"; fruits[4] = "Apple";   fruits[5] = "pineapple";
        fruits[6] = "banana";
    }

    public static void main(String[] args) {
        Sorter srt = new Sorter();
        srt.anyOldUnstaticMethod();

    }
    public void anyOldUnstaticMethod() {
        Collections.addAll(lst, fruits);
        System.out.println("Initial List");
        for (String s : lst)
            System.out.println(s);
        Collections.sort(lst);
        System.out.println("\nSorted List");
        for (String s : lst)
            System.out.println(s);
        Collections.sort(lst, new SortIgnoreCase());
        System.out.println("\nSorted Ignoring Case List");
        for (String s : lst)
            System.out.println(s);
    }

    public class SortIgnoreCase implements Comparator<Object> {
        public int compare(Object o1, Object o2) {
            String s1 = (String) o1;
            String s2 = (String) o2;
            return s1.toLowerCase().compareTo(s2.toLowerCase());
        }
    }
}

I can't believe no one made a reference to the Collator. Almost all of these answers will only work for the English language.

You should almost always use a Collator for dictionary based sorting.

For case insensitive collator searching for the English language you do the following:

Collator usCollator = Collator.getInstance(Locale.US);
usCollator.setStrength(Collator.PRIMARY);
Collections.sort(listToSort, usCollator);