Sorting arraylist with numbers in ascending form

You can create a class to handle this:

class Book {
   private int id;
   private String name;
   //other stuff
}

Then just add a new Book to your list:

al.add(new Book(1,"Romeo and Juliet"));

And just sort it using a custom comparator:

Collections.sort(al, new Comparator<Book>(){
        @Override
        public int compare(Book b1, Book b2) {
            return Integer.compare(b1.getId(), b2.getId());  
        }
};

If you really want to continue with your current approach (which I don't recommend) you could split your String by whitespaces and take the first element in the array returned by split (which assumed that your String is always in the format (number whateverIsAfter)).

Collections.sort(al, new Comparator<String>(){
    @Override
    public int compare(String b1, String b2) {
         String s1 = b1.split("\\s+")[0];
         String s2 = b2.split("\\s+")[0];
         return Integer.valueOf(s1).compareTo(Integer.valueOf(s2)); 
    }
});

Use Collections.sort with a proper Comparator

something like:

Collections.sort(ar, new Comparator<String>() {

        @Override
        public int compare(String o1, String o2) {
            // TODO Auto-generated method stub
            return o1.compareTo(o2);
        }
    });

Can you use a TreeSet instead of ArrayList? The TreeSet's structure sorts anything you put on it automatically. Also, create a class that takes the number and name separately and add those in your list instead. Don't forget to implement Comparable or a Comparator

Your problem is you're sorting alphabetically right now, not numerically, so "11..." does come before "2...". You need to parse up until the first space character, extract that content into a number, then sort by that. This should of course check that "content before first space" is a number.

All of this might sound tricky, but by writing a new 'TitleNumberComparator' it shouldn't be too bad.

Learn about comparators, and comparable: http://javarevisited.blogspot.co.uk/2011/06/comparator-and-comparable-in-java.html

you can use a Comparator passed as an argument to the Collections.sort(arrayname, compartor instance) to sort the ArrayList based on your criteria.

You can use Map and keep as a key number and title as a value

http://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html

Use a java.util.TreeMap, the number as the key, the string as the value. It will be sorted by the number "natural" order.